I've never pulled with a '45, but do have lots of time in the seat of one. I pull with a Farmall now, but can give you a few observations on using the Allis. First of all, the Allis' I've watched in pulls generally run out of traction before they run out of power. The WD-45 was a very powerful tractor, for it's size, in it's own right. If you rebuild it, I wouldn't go in the direction of adding lots of extra power. I don't think going above 50 hp will do much for you. That tractor is configured more for use with mounted implements - and the Traction Booster works well with them. You can't use the Traction Booster in a pull.
As I see it, I would recommend that you perhaps look at wider tires, and work at using that tractor in the various weight divisions. Wider tires and more weight might give you more bite. I dunno - just my observation.