Looks to me like that carb has a tiny little issue with it, lol. Either your using pure acid or creamy caramel for fuel and that isn't cutting it.
If you can get that thing cleaned and all the ports trued up it maybe ok to fix. But, I must say when you put that back on after fixing be prepared to move a lot faster then it did, sheesh that bad.
Might be better to grab a wrecking yard carb, but they could also be trashed. A weber can be found pretty cheap as well, $220 on up isn't bad for the performance you get from one, by far a weber was the best mod I put on my truck.

Oh by the way, almost forgot. That lower apron on your truck are available and reasonably price. Also Camoit had one at one time and was selling it dirt cheap. Maybe check to see if he still has it.