I don't recall if I've ever pulled the ignition coil cable from the distributor and held it near ground while turning the engine over. (Get yourself a remote starter or rig up one yourself. Ie. Push button switch with wires connected to starter). But without the "points" in the circuit would there be a collapsing field to generate a spark?

Anyhow, the Pertronix does throw off the timing. If that 10 degree timing you mention was done before the Pertronix installation, check your dwell now to see how much it has changed. I found -1 degree of dwell = +2 degrees of timing. So if your dwell has dropped by 10 degrees, your timing may be way off by 20 degrees.

If you don't have a dwell meter, you could rotate the distributor, and through trial and error see if it starts and runs at a different position. From there adjust timing.

BTW, has anyone looked into the Hot-Spark electronic ignition system? Their dwell is set at 58 whereas Pertronix is at about 50. Plus they're cheaper.
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.