The motors will stay stock but get switched to carburetors to get rid of all the electronic crap, so horsepower won't be astronomical.
Hahaha, I have a '92 S10 with the 4-banger 5-speed and she can't even get out of her own way
I don't think there is a such thing as a powerful Iron Duke 2.5.
Anyways, this sounds like a fun project! I'd try to make the frame out of steel since-
1.) steel is relatively cheap and sounds like you guys have the equipment to make it work
2.) the frame will have to be quite beefy to support that turd of an engine/tranny setup
3.) the stock engine mounts are all steel so it makes them easier to weld onto the frame
I have a few ideas on how this setup can go, and it seems like it would have to be a long and low bike. I'm curious on how to use the shifter. If you sit above the tranny, the shifter is in your crotch, and the bike has two or three feet of frame in front of you. If you sit on the engine, would you run a contraption to remote locate the shifter?
It would be neat to use a beefy shaft-drive rear end to adapt to the tailshaft of the tranny and go with a hardtail setup.
Would it be a foot-operated cable clutch? So many ideas to ponder
Good luck! I'd love to see some sketches and pics of the progress!