4 spd to auto, auto to 4spd

Somebody is working with misinformation. You should be able to make the swap with no machine work needed. The torque converter snout centers on the crank register while the manual needs the pilot bushing. Not all cranks were drilled for a pilot bushing but they all had a crank register. The register size did change, but that was between '67 and '68 not '70 and '71. You may have to install a pilot bushing if you don't already have one. I believe that '72 was the last year that all cranks were drilled and had bushings installed whether they were manual trans or auto. Hope this helps.