Backfire under loads

[liftlawssuck]

My son just got a new to him 82 K10 with a 305 and 700r4 tranny. Definitely has been messed with and trying to straighten out some things to get it on the road.

It originally had the ESC installed that was disconnected before we got it. It has TCC that is disconnected too. Different HEI was installed. A/C has been disconnected. Motor has been apart but have no idea what was done to it.

Truck ran but not great at all. After checking timing it was way off. Pulled dist. and reset. I had a way hard time setting the timing up. Not my first rodeo but this thing just didn't make sense. Eventually got it but was back at a previous spot where it wouldn't run good. Whatever...

Pulled intake and carb off and put an Edlebrock intake with a Holley carb. (I'm not looking to get into Holley vs others) Runs much much better but not 100%. Timed right up with initial at 12*. Installed new vac advance, plugs and wires.

Though the truck runs way better it still seems to be held back to me. Doesn't rev up like I think it should. When holding foot on brake and giving gas it will backfire out carb and quit.

So in all this I keep coming back to the torque converter lockup circuit. I have no experience with them so I have no idea how they work. But my gut says that if I swap it out to a manual trans the problems will go away. Though I do think that the timing chain is too loose but still.

Does the TCC stuff have to hooked up? How does that system work? This stuf is too new for me. I'm used to older trucks.

So to recap with specs:
Initial timing is 12*
Total is around 32* give or take
Idles pretty good in park. No tach so I don't know the exact RPM
Vac advance is hooked up to manifold vacuum
305 sbc
700r4 tranny
I'm guessing 3.08 gears??

I'm sure I'm missing some things but ask away.

Thanks!! Brian