Idle question

[crites_72]

I know this isnt a truck question but its on my wifes 82 z28 and if i dont get it out of the garage then i'm never gonna get to work on my truckl. the car will idle just fine as long as its in park. but as soon as you drop it in a gear it will cut out and die. i've tried switching carbs, fuel filters, everything i can think of. i've made sure its in time. its just a 350 motor with a mild cam nothing special just sounds good. when you have it in drive it sounds like the idle is to low and then it just dies. but will fire up again with no problems. right now it has a quadrajet on it but i've put a carter and an eldebrock. and another quadrajet on it and still had the same problem. a mechanic friend of mine drove it and said that it was the float in the carb but can all of them really be bad. any ideas would be great its really confusing me. thanks