just rebuilt runs bad

You are using a "dial up" timing light? That would be my no1 first suspect. I KNOW people are gonna come on here and toot their horns. But I"ve found several of these over the years that were UNRELIABLE and INCORRECT. Get/ borrow a conventional light with NO digital features

At this point, and as much trouble as you have had I would DEFINATELY find a useable breaker point dist for testing. You should be able to find a used/ rebuilt one for not much, and you can get rid of all the digital crap and SEE what it's doing.

In addition, you can STATIC TIME the points dist fairly accurately and use that as a "double check" against your light.

I understand you DID confirm timing marks with a postitive stop?

Next step IS (if using a points dist) is to double check initial timing.

You have to do this "backwards" because you don't know what the curve is in the distributor.

So first set the engine at high RPM to about 38*, then idle down and see where the initial ended up. Note that figure.

Next, you can "double check" it by using static timing

Wrench the engine around to where the intial timing showed in the first test, IE 12* or wherever it might be.

So, at this point, the timing marks are aligned, NOT at TDC, but at 12

Loosen the dist, and use a test lamp on the coil neg, with key on.

Retard the dist (CW on a SB) then SLOWLY bring the dist CCW until the points open (lamp lights)

Retighten the dist, and recheck the running timing. These figures should agree plus/ minus what little you may have fudged it. If you did this right this should be in a couple of degrees or so.

For now, with a points dist, I would NOT worry too much about initial. One thing that might help is to yank the heavier of the two advance springs off. Time it for "mechanical total" and experiment with 35-42. The engine should be sluggish and may heat less that 35, and it should ping and do other bad things over 42 by any amount. The damn thing simply should not run at all at 60 or whatever you said, which is another reason I suspect your light is AFU