Walt:
Welcome.
Sounds like a nice project. I did some work on a Buick V-6 supercharged 914, went like all get out. The gearbox is well suited to mid engine application, especially the side shifter models. I never saw a problem with breakage on that car, but the owner did start off in 2nd gear most of the time as he felt 1st was too weak, and no burnouts for sure.
There is a strengthened intermediate plate available for that trans, and the 914 boxes are readily available so you should not have an issue with parts etc.
Good luck and enjoy the forum
Cheers
Phil