Do you have a short shoe and a long shoe on each side?

You could try swapping brake drums when you have them off to look at the shoes.

You might set the wheels straight ahead as you can, and check alignment using a string from back to front

My '64 pulls to r the right on the first few brake applications. I find nothing odd about its brakes.

If you cannot find the issue, try an old NASCAR trick and wipe chalk on the linings and do a couple of brake applications to evaluate how the linings touch the drums. The shoes may not fit the drums on one side.

My dealer has a fully restored 544 and his computer guy tells me that it also pulls upon early brake applications.