The adapter plate is made from a 1/2 inch thick 6061 aluminum plate, which as mentioned previously, I purchased as an offcut where the dimensions reach exactly to the edges of the bell housing. I may only need only to trim some of the corners off, which is a significant relief as cutting 1/2 plate with home tools is a slow process.
It is critical that the electric motor be concentric with the transmission shaft, therefore I thought it best to keep the plate and the transmission indexed with a pair of guide pins. This will also allow for some forgiveness on any misalignment or play in the other bolt holes to be drilled, while not affecting the overal plate alignment.
Using a punch and a centering tool (i.e. various bits of tubing) to mark the center for the holes.
Drilling the holes. You can see why some forgiveness in hole alignment is needed, as the drill does tend to wander with this kind of set-up.
Taping the holes that will receive bolts.
Checking the hole alignment. Only a couple holes needed touching up with a rat-tail file.
Cutting the hole for the motor shaft with a jig saw. Very slow going. Applying oil to the blade seemed to help.
Finally done. The hole is actually slightly undersized, as the plan is to make the hole concentric when it is enlarged, as I will only know where the exact centre is once everything is assembled.
Now to put the transmission transmission together, which hopefully will be easier than the disassembly. Because of the erroneous directions from the Chilton manual, many loose part fell out the casing before I could see where they came from, which included 16 roller bearings for the main shaft. However, in putting things toghether, there is only room for 15 pins. I'm hoping that the extra pin was just a loose one left behind in the transmission by GM.
The main shaft, counter shaft, and gear selector mechanism before slipping over the casing.
The cover installed
Here are the aluminium couplers with an elastomer spider that I will use. These are very light, and should not add too much to the rotational inertia that the synchronizers will have deal with when shifting, as this is a clutchless system. Now I wait for my motor to come before making final adjustments to the plate.