Hmm, it doesn't sound like the 14066235 (73-81) fork will work without modification based on this post:
https://www.camaros.net/threads/clut...rewall.200119/
I went down and looked at my 621 bellhousing and fork destined for my 69 SS350 and measured the fork (no numbers on it
) and it measures 10 1/8". When looking down the center it does look aligned, but I hope it is the correct one! I bought it many decades ago!