1972 Chevy C-10 with 250 L-6

OK...I was thinking it was a dist. swap...

Is it ONLY acting up in high gear at 45MPH? Can you get it to do it any other gear/speed combinations?

Pull the dist' cap and check if there is shaft wobble?

suction

How about the obvious, the fuel pump? It sounds like a classic fuel starvation problem as I have seen before. Higway would use a higher sustained fuel flow per hour rate than town driving. Also check for a kinked fuel line, a hose collapsed internally and a even a partially plug fuel pickup in tank too. This is a fuel issue, not ignition so do not waste time chasing gremlins there.

...sounds just like the suggestions in one of my posts...

Have u Checked for intake mainfold leak!

.60 plug gap on the older hei engines

Chad Hamann wrote:

Check to see if you have at least 12 volts at HEI when running. 72's used a resistor wire to feed original coil. HEI's crap out at higher rpm if they aren't fed a full 12 volts.