Well, I don't have exact measurements but I'll tell you what I am doing. I built this set-up for my '68 Charger and I now have it on my '67 GTX. This December I am pulling the engine/K-frame from my '70 Dart and I have found that the A-body is "about" 1 3/4" narrower than the B-body. I will be using a 7/8" spacer on each side with some longer bolts to make it work with the A-body.

Aren't the E and B-body K frames the same?

Stan