Bump steer after replacing steering rack

[showdog75]

I've got a 63 Chevy II wagon LS/t56 swap with a Heidts mustang II clip. It's a very old Heidts clip that was in the car when I bought it. The rack is wore out, one tie rod is sloppy loose so I recently replaced it with a new rack from Speedway. The old rack drove and steered great with zero bump steer whatsoever. The new rack I have bump steer. The only change is I had to make a new steering shaft as the new rack has a splined shaft. I built a new shaft with Borgenson universal joints(spelling?) and clocked the joints together just like the old one. Any ideas on why the new rack bump steers? I don't understand.