318 Run like Sh*t once warm.

[NHCharger]

Coming off the highway on to another road she started to sputter, we made it a mile before she quit. It wouldn't restart. I waited 5 minutes, it started. We drove home (7miles), it started acting up again close to home. Figured I had some junk in the carb.
Cleaned the carb, changed the fuel filter, took it for a 4 mile ride-all good. The other day couldn't make it a mile. Last summer I replaced the old smogger intake with an Edelbrock, and replaced the fuel pump since I was still running the original from the looks of it, put 1,000 miles on it after the swap. The engine was rebuilt 37k miles ago. Has always run like a champ. I converted to electronic ignition a few years ago.
When I cold start it she runs smooth for 5-7 minutes. As soon as she warms up she bogs down and quits as soon as I give her any gas. She doesn't blow any smoke, I have a ½" carb spacer.
This is what I've done so far, with no results.
I have a spare carb, so I swapped out the carb.
Pulled the fuel line off the pump and ran the engine off a 2 gallon can.
Replaced coil and ballast resistor. Coil was a used unit but was working when I removed it a few years ago.
Checked for any vacuum leaks.
Radiator is full. Used a heat sensor gun and checked the temps on the hoses, heads, intake and exhaust manifolds- all good.

Any input would be appreciated.

[70 sublime]

Is the breather on the fuel cap vent plugged up ?
Try running with the gas cap open ?

[LaOtto70Charger]

Empty the tank and start with fresh gas? Spark plugs look ok? I was having issues kind of like that when I switched to a rebuilt distributor. Ended up putting the original back in. I also ended up adding a fuel pressure regulator and gauge. I had that and the filters gum it one winter.

[b5blue]

Check ALT. output and battery condition also. 

[Kern Dog]

I've had engines running with no alternator. They have ran fine.
I've had others with functional alternators but dying batteries and those ran fine too.

[NHCharger]

I just replaced the orange box. That fixed 90% of the problem. I'm now having a bog on initial acceleration, but I think that is because I currently have an 800 CFM carb on it. I'll put the 600 CFM back on it and re-tune it.

[John_Kunkel]

Your problem does sound fuel related, it could be the "sock"...the filter that's on the fuel pickup tube in the tank, they're known to clog up over time and lead to fuel starvation.

[Kern Dog]

I wish that I were better at diagnosing this sort of thing. Sometimes I get lucky though.
I had a ballast resistor issue in a 73 Challenger a long time ago. The car would idle and drive okay at low throttle but step on it a bit and the damn thing would pop and sputter. A new resistor fixed that.

[NHCharger]

Your problem does sound fuel related, it could be the "sock"...the filter that's on the fuel pickup tube in the tank, they're known to clog up over time and lead to fuel starvation.

I removed the tank last year and cleaned it. Took it for a short spin today. sputters a little bit on take off but no issues now cruising or nailing it at 30. Need to drop the smaller carb back on it and do some tuning. The oragne box was the original one I installed when I converted to electronic ignition 20 years ago, so i got my monies worth out of it.