Needing help and it has nothing to do with my age!

[Jim Boy]

Good day folks. I have a brain burner going on. The story.. 68 truck ran perfectly to the golf course. On the way home it started to backfire on acceleration. I though it was mad at my score but it continued all the way home. So I thought that with the crappy fuel we have nowadays it must be in the carb. I had a kit so I rebuilt it. Fired up the money pit and it ran perfectly until it got hot and then the same problem occurred. I talked to a few knowledgeable guys and they said carburetor. So another kit and dider again. Same thing, no worky right. So there was two choices. Either beat the heck out of this money pit or be nice and spend some money on way overdo items. So I chose the latter and did a lot. It got new points and condenser, new coil I had in a box on the shelf, plugs and timing done. I even replaced the carb that c/w automatic choke for my old one from another engine that c/w manual choke, that engine ran perfectly. Same result.
So the 250 engine is idling for quite awhile while I'm standing there reading about the different needle movements on a vacuum gauge, when the engine just chugged a couple times and quit. We stared at each other for a while as I was not going to let it win. I figured that it ran out of gas from the carb. I took the top of the Rochester Monojet off and when I lifted it up the gas gurgled into the fuel bowl. Now I'm a thinkin that I either have a stuck needle valve or my fuel pump is not doing the job after it has ran for a while. When cold, the engine will accelerate like it should but when it gets warm, bingo, bango, no ticky no worky.
That saying of "less is more" doesn't apply to old farts that like to talk(or type) as you probably have noticed. Just trying to eliminate questions. I will treat all replies with great interest and report as to whom is the winner.
Have a good day eh!