RF brake locked up. Why?

Okay riddle me this. On my numbers matching all stock 68 Dart GTS. I've been following this because I've been having the same problem with the right front brake locking down more than the left front and pulling strongly to the right.

That is until I drive a while and everything seems to warm up and presto... both the front brakes pretty much brake about the same. Maybe a little bit more on the left.

I've bled the brakes.

I have replaced the front rubber brake lines with stainless braided lines.

All hard brake lines and the front brake proportioning valve (wasn't sure the original would work after being on jack stands for 25 years) were replaced a few years ago and used copper gaskets on all fittings as suggested by someone I don't remember that does restorations because I used Dot4 synthetic.

Any ideas?