Aside from my message below, re that emission testers may not like your aftermarket equipment...

I recalled that, when I used to have a 1973 164, B30F engine, I had worked out the advance curve. Realize that I measured it (with a timing light, as was suggested -- mine had an advance "wheel" that I could turn to rezero at each rpm, hopefully for more accuracy -- but it was a home-made unit, a "HeathKit" electronic project kit, so I can't promise exact accuracy.
But I've found the graph that I made and kept tucked inside my '73's "green manual" (I never throw things away).
So if a B30F (instead of your B20F) is of any help:
[Note: I did not record the overall BTDC, but only the amount of advance, or how much BEYOND the BTDC at idle -- I was planning to fiddle with the advance curve using different springs]
Here are the empirical data points from my graph:
At 400 distributor rpm (double this for engine rpm), 0 deg advance (over idle advance).
at 500 " " , 1.5 deg. more
at 750 " " , 5.0 deg. more
at 1000 " " , 7.5 deg. more
at 1250 " " , 9.0 deg. more
at 1600 " " , 10.2 deg. more
and it leveled off beyond that rpm.

Even if not exact, it should be within the ballpark, I think.