I installed one in a '70 Challenger and I can say based on experience that the tunnel need clearancing. You will probably need to hammer clearance into the tunnel. Also, if you are using the stock floor shifter, the shift linkage needs to be bent to accomodate the larger/thicker tailhousing. The lower shifter mounting bracket won't fit unless you grind material off the mounting flange. You will need to check for clearance between the transmission x-member and tailhousing because of the added thickness tailhousing. I needed to use an updated urathane mount to keep it from ratteling against the x-member.