Basically, I am building my own bellhousing to adapt a Ford Toploader 4spd transmission to my old school SB Chev V8. I can buy one for around $600, but it's a heavy 1/4" thick steel monster, and I prefer building my own lighter parts if i can. I'm not concerned about it not being "SFI certified", as it's just a fun street car and i have no desire to make it legal for the track.

The mock-up began with an old 400 block and an empty transmission case. I am using the alignment bar from my rearend narrowing jig to keep everything straight and true. I spent a couple nights machining some steel pucks to fit in the block's main bearing bores and also the bearing bores in the transmission case. The pucks have an 1.501" hole in the center so that my alignment bar will slide inside everything to keep the engine and transmission bores concentric. I made a ring to center the plate that the transmission will bolt to, and a tube spacer that will set the desired distance between the block and transmission face. I have also made the rear plate that the transmission will bolt to, and have laid out the the flange that will bolt to the block and serve as a pattern for the block plate that will fit behind the flywheel.

I'll snap some pictures in the next day or so. Working in my spare time after hours, I expect it will take me a week or two to get it done. The transmission is getting some special work as well, getting faceplated in 2nd, 3rd, and 4th. I'm adapting an aluminum tailhousing from an SROD overdrive trans to replace the Toploader's stock iron piece to shed some weight. Also machined down the Ford throwout collar so that I can use my existing Chevy hyd throwout bearing.

Here's the pattern I made out of 1/4" steel. All the hole locations were laid out, centerpunched, and drilled 3/16" so that the pattern could be transferred to the blank piece of 1/8" that it's laying on, which will be used to make the block protection plate. The steel pucks on the right are the pilot rings for the alignment bar which makes sure the block and transmission centerlines are concentric. The tall depth spacer is actually 3 pcs. The lower sits against the face of the block, the upper sits against the front face of the transmission, the center is a 2-1/2" x .065" tube. Length of the center tube sets the distance between the back of the block and the face of the transmission. Later this pattern will get the bolt holes drilled and the large center hole will be cut out, turning the pattern into the flange for the front of the bell...

Here's the drawing I used to lay out the block bolt pattern...

This is the block plate after it was cut out and drilled. The large hole in the center is for the crank's flywheel flange to stick thru, and the 2 larger holes on the sides are for the locating dowels in the block...

This is the pattern after i drilled it out and cut the center out. It is going to be the forward flange of the bellhousing that bolts to the block, the large hole in the center is necessary to clear the flywheel...

Here's the block plate on a block. The upper "wings" were added as mid-mounting points that will hang the back of the engine at the firewall...

Here's the block plate and flange on a block. The block plate will be sandwiched between the block and bellhousing as shown. I'll soon be creating a hole and pocket for the starter.

Here's a pic of the rolled ring welded to the bellflange. All the holes still fit perfectly...

The mid-mounts incorporated into the block plate allow me to easily remove the bellhousing/clutch/flywheel from the car without needing to support the engine. Greatly simplifies my clutch and transmission maintenance.

Here's the alignment bar in place in the block, as well as the spacer that sets the depth between the block and trans case...

Here's the trans case in position located by the pilot rings...

I had to take it out of the fixture to make sure i had created enough room to install a SoftLoc clutch, so i figured i'd snap a few pics of the progress.
I started making patterns for closing in the bell by laying out the the top section on posterboard. I quickly realized it was much easier to just cut out slightly larger pieces of posterboard, hold them in place on the bell, and simply apply a little pressure by running my finger around the edges of the steel. This puts a small crease in the posterboard and transfers the exact shape needed, a much quicker way to create a pattern...

The transmission plate is still only tacked in 4 places. After all the rest of the welding is done, i'll put the bell back into the fixture, cut the tacks, and re-position the plate for the best alignment possible before welding it in place. I doubt there will be any need to machine the block or transmission mating surfaces.

Still need to make a pocket for the mini-starter that's going on the car...

Added a cutout for the mini-starter's drive...

Added a starter pocket to the bell as well...

At this point all the welding will be finished up with the exception of the transmission plate. The last part of the welding process if cutting the tacks that hold the trans plate in place, then re-installing the bell on the alignment fixture to ensure proper alignment before welding the trans plate to the rest of the bell. Also adding a few holes, one for setting the clutch gap and a hole for the hyd t-brg's hose.

Here's the finished product...

UPDATE-...I went to a 3pc style bellhousing...blockplate, midplate, bell/can. Now i can remove the engine from the car with the flywheel and clutch, and leave the bell and transmission mounted in the car. I can also remove the transmission/bell/clutch/flywheel from the car without supporting the rear of the engine. I also added a couple external "ears" to the block plate, which gives me some easy attachment points for lifting the engine.
The finished bellhousing itself weighs in at 16.3lbs. The Mcleod aluminum/titanuim bell is only 1.5 lbs lighter!!! The entire 3 pc assembly shown below, including the block plate, midplate, and bolts, weighs 26.2lbs.

Here's a pic of how/where the midplate's "ears" attach to the RX-7's relocated firewall...

This shot from the inside shows one of the aluminum firewall reinforcements installed behind the firewall. They serve to spread the load over a wider area so that stress transferred from the midplate does not buckle the thin stock firewall's sheetmetal...

I'll take some pics of the engine lifting fixture i made for it. It plugs into the blockplate's added "ears" and into an "eye" that screws into a hole in the top of the waterpump. It fits over the complete engine with the aircleaner and distributor in place. Before i was always using some type of hokey chains trying to find a perfect balance point without damageing something. Now i have a dedicated fixture that plugs in and makes the job easy. Been thinking about attaching the radiator to the engine just to make choosing between a couple engines that much easier

I'll take some pics of the engine lifting fixture i made for it. It plugs into the blockplate's added "ears" and into an "eye" that screws into a hole in the top of the waterpump. It fits over the complete engine with the aircleaner and distributor in place. When using chains, finding a perfect balance point without damageing something can be a challenge. Having a dedicated fixture that plugs in makes the job easy. Been thinking about attaching the radiator to the engine just to make choosing between a couple engines that much easier