The next mount that I needed to fabricate was the rear mount. This mount, coupled with the front mount, resist the torque produced at the axles. These two mounts are completely responsible for keeping the engine and transmission from rotating due to the torque generated.
The GM F40 6 speed manual transmission (transaxle) that I am using has provisions to bolt the mount to the rear of the transmission case. I decided to use a square-ish rubber block type of mount commonly used on domestic muscle cars, under their transmissions. In essence, the drive train would be trying to squish this mount when the car is accelerating. This mount attaches to the top-side of the removable cross member at the back of the MR2 Turbo. I basically copied the way Toyota did it, because Toyota did a great job figuring out these mounts. I could not easily use the original Toyota MR2 Turbo mount because it was too tall. I had to drill a new hole in the cross member to bolt the rubber block into place.
I then moved on to the right side mount. This is the only mount that is directly attached to the engine block. GM did not really intend for a mount to be located here. Toyota did on both the 5SFE (base engine) and on the 3SGTE (MR2 Turbo engine), and so there is a provision on the blocks of these engines to attach the mount to. I needed to figure out how to attach a similar type of mount to the Cadillac Northstar V8 that I was using. I also needed to get rid of the power steering oil pump that comes with the engine. The MR2 does not really need power steering, and while some MR2's were opted with power steering, they used an electro-hydraulic setup, where an electric motor powered the power steering pump, and both of these were located at the front of the car, in the "Frunk" or Front Trunk. I mounted a dummy pulley in place of the power steering pump on the Nortstar. It was mounted to a bracket I fabricated to fit in the valley of the engine. I was able to attach this bracket to the rest of my motor mount. I found some screws and tapped screw holes on the block that could double as attachment points for my mount, so I fabricated another bracket. I was able to bolt the two brackets together, making for an extremely strong assembly. I then was able to weld a tube to this bracket, and install some urethane suspension bushing inserts into the tube. The tube and bushings were located on the engine, so that they lined up with the engine mount ears that are part of the structure of the MR2.
Now for the hardest mount of all, the left side transmission mount. This required quite a bit of head scratching for me. The transmission mount ears that are part of the structure of the car on the left side were now near the mount attachment points on the transmission case. The ears were over the top of the transmission, and the transmission attachment points were on the bottom left side of the case. I decided not to use the ears that were on the car. There simply was no way to use them. Instead, I created another nut plate, and welded it to the bottom of the chassis pseudo-frame rail. I was then able to fabricate brackets and use another rubber square-ish block to provide vibration isolation for the transmission. I was able to place the block so that one side of it pushed on the side of the transmission case, effectively wedging the transmission into place so that it could not move to the left under cornering. The right side mount preceded the transmission from moving to the right under cornering. I was able to set up both the left and right mounts so that the engine and transmission could rotate a very small amount during acceleration and engine braking.