I've swapped distributors before to diagnose an engine issue and the rotor vs the tang were oriented differently. Gotta watch for that. Both distributors were elec ignition.
I put one of those POS Pro Comp distributors on my car one day and it ran like **** at low R's.
Come to find out the rotor tip was damn near at the number 8 contact in the cap when the distributor was supposed to be firing number 1.
Once the centrifugal timing started coming in it ran ok.
I had to pull the pickup out of it and drill new screw holes for the damn rotor to be pointing where it should when the reluctor points lined up.
Then after all that I threw it back in the box and shelved it marked POS distributor that works now.:D
I was doing it to possibly be able to run the red male terminal cap and 10.2mm Dragon Fire wires using a Ram C core coil.