Timing running at 20* advance...

Here's a little background on the car. 1970 Duster, low mileage (73k), untouched, that has sat for years till this summer. I bought the car in June this year it would start and run with gas being poured in the carb. I have gotten it road worthy. It runs and drives really, really good. In order for me to be satisfied with the slant, it will need to be modified. It needed a tune-up as you could guess, so an HEI conversion was sourced. Distributor from @halifaxhops , Standard ignition products throughout, ran by a Bosch relay.

The day I started swapping in the HEI I checked the timing and it showed 0* TDC (like the sticker says on the inner fender) on the old distributor. I set the engine on TDC, marked the rotor position, did the wiring and set the new distributor in on the mark I had made. I know it doesn't matter where you put the rotor, but I'm a little OCD about things. The car would not start, so I pulled the distributor and moved the rotor back a couple of teeth (retard). It would start but not run good. I did that again and it started and ran good. I set the timing then at 5*.

Road test, not good. It idled fine, but would not pull good. I stopped a couple of times and adjusted the timing (advanced) to where it runs way better than it ever has. It will actually boil a tire while turning (and without turning on smooth concrete). It idles great, so good in fact that yesterday my wife was in the shop leaning against it and didn't know it was running.

So, yesterday I decided to see where the timing ended up, 20* BTDC. That's initial, vacuum advance not hooked up. It has a total advance of plus 30*. Doing searches this morning, but can't find a similar situation. I'm going to throw a lot of mods at this thing to make it acceptable to me. Any ideas?