The frame mounted "L" brackets that support the C4 transmission's cross member are slightly different dimensions. I didn't take note when I removed them. On the top, one is 2 1/2" wide, narrowing to 2". The other is 2 1/2 inches wide the whole length of the top portion that supports the cross member. The dimensions of the engine motor mounts in relation to the frame are different so I'm guessing the trans. supports may be side specific as well. Anyone in the know? Thanks