The crank pilot hole changed in 1968. The 67 and older has a small pilot and requires a flexplate and converter to match. 68 up have the more common larger pilot. I ran into this when I went to buy a performance 904 torque converter and was using a 67 engine and a 71 transmission.
The first and biggest reason why I pulled my 170/6 out of my 66 Valiant, it was a great engine and I needed to get rid of the standard :pale: small pilot hole :banghead:
