New lad with 69 camaro ss

[twicx]

Hello all!
I'm new, from Ireland, on a big fact finding mission for an ambitious 69 camaro ss project. I'm working on the budget for it, but it'll be some sort of engine swap, and some upgrades to the drive train too. The plan is to get the major stuff like engine and drive train done by a custom shop, and do some minor stuff myself, more suited to my knowledge.

So, first query I have, if I planned on changing the whole drive train, obviously wheelbase and width is going to be one of the major deciding factors. How much tolerance do you reckon I'll have?