I have a 69 R.R. it used to be 440 auto and I jerked the 440 out and put a rebuilt 383 in to make it more original. It has a engine harness from Bill Evans that switched the points over to electronic. It ran and performed flawless. When I put the 383 in I had to get a new electronic distributor, I got it from advance. Put it in and no start, no fire, and when the key turns off it tries to start. So I took and back and got another. Same issues, so I went to napa. Now have the same issues again. Im stumped, Everything is the same and I have a customer car here that has a billet distributor in it and vacume advance, I put his in and it started right up. Put my distributor in his car and after cranking and cranking and trying to turn over when the key turned off it finally started up. Anybody ever had these issues.

Try a new ballast resistor.

Sounds like a balast resistor or voltage issue.

In other words , one distributor with work with lower/higher voltage and the other does not. It could be your ign switch too. Because it has 2 distinct circuts when in crank and run. So, maybe no circut when in crank, but then you get votltage when you go to run (release the key).

You need to get a meter and start testing these circuts.

Check the rotor phasing. Make sure the rotor is inline with the plugwire post when the reluctor wheel (trigger) is lined up with the distributor pick-up coil.