The '70' and early '71s differential strap sits forward by about 2 inches compared to later 240 models (different brackets). So if you try a R200 swap on an early cars, the R-200's front mount nuts on the top will hit the strap. I found I had to reverse the bolts, place the nuts on the bottom, and saw off the protruding bolt threads so the mount would flex. I then raised the differential with my floor jack, and placed it very tightly against the strap. Only then was I able to bolt the front crossmember in. Since later 240/260/280s's had different strap brackets, they won't have this problem.