Shift linkage troubles!

I have a fresh built 727, shift kit and all. I was going to do the same swap as you, so I looked into the linkage, and found out there are some differences. The exact difference I am not sure, but do know there are some differences.
I think you have found one of them with the frame to trans linkage.

The linkage out of a A-body 340/727 is what is needed.

Wish I could be more help.
I just decided I am going with the 904 on this build, since I have all the parts for it..