[Sid Squid]

Electronic parts don't like low volts, when trying to start a Pointy with a low battery the terminal voltage drops away quite significantly - which explains why the dash flashes on and off.

The charging voltages you've posted are low, thus regulator is suspect. all the same it's well worth checking the stator which is easy:
Identify the three alternator output wires at the regulator, call them A, B and C, rev the engine to 5000 rpm and check voltages between each pair; A+B, A+C and B+C, each pair should give approximately 70VAC, +/- a bit, but all three readings should be essentially the same.
If the results you get are substantially different, or if one reading differs from the others, check the stator resistances between each pair and between each wire and a clean bare metal engine case point. I can't remember the exact winding resistance figures but it's something like 0.5 ohms, again all three readings should be essentially similar, and between each wire and ground should be open, that is no connection at all, if you find the winding readings good but one or more goes to ground check the wiring between the rectifier and the stator very carefully.

Stator failures are rare, wiring, connector and regulator problems are more common.