Is it the original linkage? 904 won't work right for a 727 and vise versa.
My 72 had a 904 originally. When I restored it, I bought and installed a 727. When I went to install it (using my 904 linkage) I had similar issue as you are having. Once I got the 727 linkage, it was easy to get it adjusted properly using the lower rod.
Other than the painfully obvious fact that the indicator doesn’t line up with the PRND21, is there any other sure fire way of know what linkage I have. I can post pictures for any transmission savant.