I had a look at the 123 site & all the info is gone like you said. The info that was there was just initial & total for all stock engines & the same stock engines on LPG.

From a 1973 Volvo Greenbook:
10° Initial @ Idle
Centrifugal Advance:
Advance begins @ 375-550rpm @ Distributor
5° @ 800-970rpm @ Distributor
7° @ 970-1140rpm @ Distributor
9° @ 1200-1375rpm @ Distributor
11° +/- 1° 1380rpm @ Distributor

Averaged out @ crank rpms:
Advance begins @ 925rpm @ Crank
10° @ 1770rpm @ Crank
14° @ 2110rpm @ Crank
18° @ 2575rpm @ Crank
22° @ 2760rpm @ Crank

So, I would go 10° @ 0-1000rpm @ Crank, then a straight line to 32° @ 3500rpm @ Crank.
NGK BP7HS Plugs.
Depending on how good your fuel is, keep upping the speed of the curve until you hear it ping, then take it back a couple of hundred rpms.

FYI, B20F specs are 34° total @ 5000 crank rpm.

The total timing depends on cam, compression & octane rating. If the fuel is subpar, you may not be able to use 32° total @ crank.

So you have a B20B head shaved to B20E (& using the thin headgasket I hope)
42mm or 44mm inlet valves?
Where are you hoping to go to with this motor?

"Standard B20 block, D-cam, 2" exhaust, 4-2-1 manifold
B20B big valve head, port matched, shaved to B20E spec"

That should be 10.5:1.

EDIT: Found this https://www.123ignition.com.au/wp-content/uploads/2017/09/123-VOLVO-B18-B20.pdf