Like to get an idea if there is enough interest in a cast AL bell housing to mate the 4200 to either a T-10 type bolt pattern or a T-5?

Maybe a steel can should be made instead. These engines will be hotrodded and the blow proof housing would add safety.

efi,

What tooling is involved for the cast aluminum? Is it lost wax using rapid prototype methods, hard patterns, or?

Steel bells are deep drawn stampings and require significant tooling dollars. Maybe there is another way.

How about aluminum plus a blanket for safety? Perhaps the buyer is required to purchase both.

Hard patterns. Factory bells are cast AL so for most folks it will be fine.

How about a cast front-facing intake manifold?

Back to the OP, the old transmissions were best IMO because of the strength and ratios. The BW T10 and Muncie M22 are examples.
First gear starting at 2.2:1, more common 2.5:1
The best T5 is almost 3.0:1 and is weaker.

I've got the adapter now from Two Trout and the 4speed and the bellhousing, so I have little interest.

How are the pans coming along?

Talked to the foundry today, said to call next week. Looking to get qty. 4 cast.

Could you design a bellhousing with variable depth ie modular for new and old transmissions?