My car developed poor fuel economy, and the culprit is the vacuum advance, whose function is said to be vital for good fuel economy when cruising at light load.

The distributor (Bosch 0 237 002 010 - reluctor type) vacuum advance cannister on my 244GL K-Jet B21E developed a leak such that when pulling a vacuum with a syringe, it leaked down from full advance to zero advance in 2 seconds, so is kaput. (It has only one diaphragm - advance only type distributor)

Can't get replacement from Bosch (long obsolete distributor) or from pick-n-pull which has mainly B21F distributors (Bosch 0 237 002 039 - reluctor type) (or a few B230 dizzys). Should I just put complete B21F dizzy in B21E - or will this reduce power and fuel economy?

Or is it OK to "compromise" and put a vac advance cannister from a B21F into a B21E, the main difference in cans is that the B21F can has max 15 (crankshaft) deg advance, but B21E can has max 10 (crankshaft) deg advance.

Comparing OEM B21E, B21E modified, and B21F dizzys total max advance in degrees:
B21E OEM: 8 (static) + 32 (mech @ 4000rpm) + 10 (vacuum) = 50 deg
B21E Mod: 8 (static) + 32 (mech @ 4000rpm) + 15 (vacuum) = 55 deg
B21F OEM: 8 (static) + 27 (mech @ 5000rpm) + 15 (vacuum) = 50 deg

Is 55 deg max possible advance likely to damage the engine? Car is high mileage (535,000 km) so compression must be down, but had head shaved to fix coolant & oil leak (was slightly warped) so maybe increased compression to original spec?).

Or do I have to get remanufactured distributor for B21E engine from United States, if available? Plus big cost to ship by FedEx to Australia.