3B was just here the other day talking about different cross members and various other modifications folks have done to their trucks for conversion to V-8s and knowing Bobb he is a wealth of information on all things GM and would be a lot of help to you... unfortunately I don't have a lot of advice to give you as my '37 was purchased the way it sits, 350 already installed... I had nothing to do with that conversion and given my mechanic abilities it's probably a pretty good thing too!
If anyone can give you good accurate information on the subject it would be him... he usually lurks around these areas of the forum so hopefully he'll spot this and respond... if not send him an PM and he'll have you on the right track in no time...
Good luck!
~Trev
