[Gaz64]

Steve,

For any conversion to electronic timing using a distributor, especially if using multi-spark, the rotor phasing MUST be addressed, either with an adjustable rotor, a phaseable reluctor wheel or an adjustable trigger sensor plate. I use a spare distributor cap, drilled with large holes to verify phasing with a timing light.

With potentially 30 degrees of advance, (mechanical and vacuum), cranking at 10, idling at 15-20, WOT 28-36, cruising at 40+, you can see the "sweep" the rotor button takes.
The target is to have the middle of the curve centre on the terminal, so half of 30, 15 + 10 cranking = 25

So at 25 on the balancer, the rotor should be centred on the cap terminal.

Your own figures could be different to my example.