If memory serves correctly, there's no need at all to alter the supply, even with a ballasted system, when converting to Accuspark electronic ignition.
Nothing wrong with Pigeons circuit but almost certainly not needed - check with Accuspark that they have a module suitable for a ballasted system though in case i'm speaking out of turn.
Bosch distributors are notorious for closing the points gap despite proper and careful initial setting. Don't forget a smear of high melting point grease on the cam lobes of the shaft to prevent premature wear on the points heel and once you've set the points to where they should be, check the stroboscopic timing and adjust if necessary.
If you want an unobtrusive conversion, it should be possible to find an electronic ignition set up from a later 240/early 740 with the dizzy mounted on the block (as opposed to the rear end of the camshaft) and convert it that way.
Maybe not as cheap as the Accuspark but would be Volvo branded bits throughout.
