From discussions on this board, "it might be" that other dists besides Pertronix are not necessarily clocked as per original.
"Someone else" mentioned that the distributor gear/ rotor "can point to China" and the thing will still run FINE
Hell, my first 57 Chev, I wasn't even aware that there WAS a "correct" way to orient the rotor. I still remember a gas station jock who was checking the oil, tell me "It can't run, the distributor is out of time" after I had just driven the car into his station!!!!
Now this DOES MATTER on some engines. The "odd fire" V6's and some 4 whangers have every other pair of cylinders firing close together, with a big wide space in between. But "traditional" straight six's and V8's don't matter in the least