we put a 460 in one a while back. we used new motor mounts cant remember what years, and hooker headers that were a PITA to install. And also had problems with the starter for clearance with the c6 we used cause of the tight fit. I would for sure use a Kmember if you can find one or like said, motor plates.
Honestly, i would get a JE bell for FE to c4. or glide. smaller and better. IMO