Stock heads but I can run a roller cam, which I will do next year.

That would help and some GM rectangle port iron heads would help too.
I'm assuming the 781's are oval port.

yes they are ovl ports but with some work they will be fine builder was think they would have more torque at the end of the track so it wont fall on its face

The 781 oval ports will give you more torque and lower end power. Put some bigger valves and some port work and i think these heads will work better than the 990 heads. Good luck ejm and have some fun.

well got her going and wont really idle right and went down the track great but header glow at end of track any ideas

check your exhaust gas temps
check the timing it maybe running rich and the timing may be too far retarded most common cause is not enough timing and too much fuel

I had total timing set at 30* think I should go higher?

I would start at 36* and work from there in 2* increments up or down.

maybe thats why when it "dogged" down at the end it flat out almost died under 3000 rpm (dist not locked)

How do you leave the line when pulling? Do you foot brake and at what rpm?