do i have to cut the firewall to use the factory subframe? do I need to make a new oil pan to clear the steering rack if I do use tha factory subframe? obviously bumpsteer would not become a problem but would I throw off weight distribution or have clearance problems with the hood?

 

If a FD is what you got, Defined Autoworks has done all the math for you. No cutting required. Yes the pan gets modified a bit, as well as a couple of other things. Check out their thread. https://www.rx7club.com/defined-autoworks-176/defined-autoworks-20b-conversion-kit-644417/

 

Sticking the larger, heavier, and longer engine in the stock location will change the center of gravity. This is because you are moving the weight higher and furthure forward.