Engine starts up and idles fine, but when the auto tranny is put into drive or reverse, the motor dies. What do you guys think, maybe a vacuum leak? or maybe the carb? This is not on a camaro, its a 73 buick regal with a 350. I am trying to help him out, but I am stumped.

probly a blown modulator on the tranny

Is there is any way to check that out without buying a new one?

does car have a big cam? if so mite need a stall converter.if not check for vacume leaks or mod.valve

No, it doesn't have a big cam. It's all stock.

Vacumn Leak is the first place I would start. Second is the modulator

1.Vaccume leak
2.Too lean
3.Timing too low
Just my opinion, it will one of these 3 issues.