Backfiring out carb and wont run right

Either you have a timing problem, or a vacuum leak.
I know you chked the timing, but what else has to be timed? (The cam)

Just make sure you double chk the easy stuff first, like firing order on the plug wires and so on.

And yes, make sure your accelerator pump works right first.
I was under the impression that it was totally undrivable.