Does any one have a Prestolite service manual that may shed some light on letter codes on distributor parts. Cam Stops stamped with letters like A, AA, B, E, W? What do they mean, I assume it has to do with slot length?

Also shaft have various letter for similar Big Block distributors. Like 39LC 39LA. And part numbers like IAZ1039L and IAZ1139L

Pretty sure L is left and R are right for rotation, but did a 1139 supercede a 1039 or is it a different part?

I have found subtle differences in shaft length and corresponding difference in common cast bodies (IBP-1), also clocking difference in the shaft to cam.

So I was wondering if some one with a service manual can find out if these codes where discussed to help decipher parts. Thanks,