I'm getting ready to do the same thing 70 Challenger with a hemi and shaker using a B/RB K frame. I called and spoke with Schumaker about the issue, and they say buy the mounts and install. If there any issues they will address the problem with whatever you need to fix it...ie. 1/2" too high or right side sets too low etc... The assured me there would be whatever support I needed to make it work! So, I bought from them.