im in the process of doing mine rite now. if you want it to be flat on the belly you need to make a new trans crossmember i used the fror style mount then you need to cut out the floor some to clear shifters and the new mount. i made motor mount spacers to keep my motor level but i dont think you have to do that. mine is with dual cases and first gen it may be easier or harder with a single case and depending on year.
