out of gas?

[Gearhead999]

First you should start at the beginning. Try taking the gas cap off car and see if it still "runs out of gas". Tank has to be vented.
Second, test the fuel pump at the carb before and after it acts up for both pressure and volumne.
Third, Are you sure it is running out of gas?? If you can duplicate it in garage. Spray some starting fluid or such in top of carb when it starts to lay down and see if it picks up.
If all this is OK, one through three. And it does pick up when you spray it. Check vacumn for leak.
Finally try another carb or raise float levels. You have eliminated everything else. I know you said that carb was "rebuilt" by pros, twice. But, maybe carb casting is bad.

Let me know how you make out, or what you find.