if i mash on the gas , part of the time it has a stumble then accelerates way good, it is a carbed car, again, it only stumbles like that part of the time

check your carb.
chances are one of two things though others are able to happen
vacuum leak and accelerator pump.

it is prolly one of those two things.
other then that it could be jetting but I almost doubt it if it is a "sometimes" situation.
vacuum leaks are a bitch. they don't effect you sometimes and other times they make the car hardly run.
accelerator pump might just be a little worn also causing intermitent issues with it not sealing right all the time.

If it is a factory carb, it's a q-jet, the secondary throttle plate could be the problem. It's likely that it's opening late, the fix is rather simple though but it's time consuming. Check out quadra jet tuning tips to get a detailed explanation of tuning. I'd like to help but i haven't had to tune the secondary throttle plates yet.

would that really cause it to sumble or just run like it's missing some pep?

it is a 3310 holley 750 vacuum secondary carb

Sounds like either acc pump/cam not set up properly or secondary opening too soon.

What is the rest of your setup? Cam, tq convertor, gears, intake, comp. ratio., timing, etc?

i just bought the car but it has a golen crate 350 hp 350 i did some research on it, and if they used the same cam now it is a comp cams xtreme enrgy 268, 3,000 stall convertor, 3.73's, performer rpm intake, 9:1 compression, and the timing i believe is 10 degrees initial, 34 degrees total

If it were me, I'd play with the pump shooters first. That's pretty easy.

Hard to say if smaller or larger is the way to go. Sometimes you can get some direction by having someone watch the exhaust. If it lets out a cloud of black smoke when it stumbles, then maybe too rich and try smaller on the shooters.

Was it a "tuned" combo including carb?

it is tuned to the spec sheet for the motor, but it has sportsman 2 heads instead of the 70cc combustion chamber gm heads it came with