Truck runs fine for about an hour or 90 mins then dies

[Juiceball]

Anyone had this issue? My '83 K20 has an older 454 in it with an HEI. The truck will run fine for about an hour or so then sputter and die. When it starts to sputter, there are surges of power like the spark is flipping on and off. When it dies, it will start again after a while but won't run again without sputtering and dying until it cools off for several hours. I changed the ignition module and switched coils (using an old coil from another Chevy that runs fine). Going to put a new cap, rotor, and coil on just to be sure, but I'm thinking it might be the condenser? Will heat affect that and would it even be the cause? Could it just be a bad wire somewhere that is getting hot? When it runs it runs fine, smooth, and strong so I don't think it's a fuel issue, but maybe?

Thanks, I'm stumped!