John,
Re: "Currently I have to choose between slightly retarded timing and stronger low end punch or slightly advanced timing and more high end power." I pulled a Bosch 0 231 153 009 distributor from a, what I guess was, a "65 - 67, 122. This is a strictly centrifugal advance unit, and can't find any reference to it in any of the Volvo sources. The closest I have come to finding its identity is that a distributor with the same number was used in VW Type 2s. I've now got it in my PV with a Crane flasher. I set it initially with 20º at 800rpm and it didn't stop advancing till well over 45º at 3200 rpm -- way too high, Phil Singher told me. So I've been backing it down gradually, and every time I back it down, the car seems to run better. Now I'm at 5º BTDC at 800 rpm and it tops out around 35º at 3200 rpm, (can't tell precisely because the crank pulley is only marked to 30º) and the engine seems to running freeër than ever. Perhaps one of these distributors would do the job for you, if you can find one. I have a hunch that the 003 may be similar.
Bob S.