[yblock57]

Just spitballing here... I had a similar intermittent miss on the 272 in my ‘56 f100.

Turned out to be two bad plug wires. They all tested fine when Ohmed, but pulling one at a time from the cap at idle revealed 2 that made little difference.

I keep a couple of long plug wires around to help me diagnose that sorta stuff.

If your ignition parts don’t make any difference, I’d at least try pulling each wire off and see if you get the same bog when each cylinder is dropped.

Good luck