I was told that the frame is narrower on
s series cutlass's , and that headers would not fit the olds 455 in that car. Its a 72 cutlass supreme convert. The tech guy at summit said this to me. Why would gm change the front frame rails and crossmember on this , but other cutlass models, and 442 can run them . The only diff. in the frame should be extra body mounts for the verts and maybe extra boxing in the rear rails. Has anyone accomplished this or can I modify the crossmeber or rails by a simple notch or what?????