Marlin 60 and Red Dots

I have a BAS red dot like the Tasco BKRD3022. Since day one when mounted to my
Marlin 60 dovetail the sight is slightly tilted to the right. I even just got new clips for it from BAS and they do the same. BSA has not been much help. Does anyone
know what's up with this and is the Tasco a better fit? It appears the clips should
be slightly shorter where they grip that side of the dovetail.

It probably has to do as much with your base as the clamps on the sight. I can't tell what sight will be exactly straight on your gun. This is not an uncommon problem, but fixing it is something found out through trial and error. Generally a full size weaver base does not exibit such canting as found on 3/8" dovetails.