1972 c10 350 surging under heavy acceleration

[Mike_The_Grad]

Hey everyone, so my truck will start surging heavily when I mash the pedal. It does not always do it. I first noticed it about 2 months ago on a real hot day. Like high 90s. I could not go more than slight throttle or else the truck would start bucking and surging. Never stalled, never died, did not over heat, had no issue with hot starting or vapor lock. Yesterday I drove it around and gave it a good flogging. The first hour ran perfectly no issues. After I parked it for about 2 hours and the outside temps went up, me and a buddy made a hardware store run and the truck did not like anything over half throttle. Even if i got into the surging and tried more throttle or less throttle it still surged. Basically forcing me to do the posted speed limit. Not a bad thing at all, but i wanted to show my buddy what she's capable of. Oh well no problem. But the surging thing shows itself at weird times and sometimes when I need it to perform.
What would cause this intermittent surging issue? Here's some info on the truck: 350 4 bolt main, bored 0.040 over, flat top pistons, 041 cylinder heads, CR at around 10.2:1. Obviously running only premium gas forever. Roller tip rockers, edelbrock performer EPS intake, edelbrock 1406, rebuilt about a month ago, fully calibrated to run as rich as I could make it with their calibration kit, yes I know this is not good but I have already blown a head gasket 2 times in the last 5 years, cam is elgin 1875= 1/4 race cam, davis Unified iginiton distributor custom tuned for my truck, headman elite ultra duty headers ceramic coated, 3" super 40 flowmasters dual exhaust, truck has been fully rewired, trans rebuilt less than a year ago, th350 with shift kit, 3.08 posi rear end with new ring and pinion, caltracs traction bars, long bed. Truck is fun as hell to drive and my only vehicle daily driver. Also has dual electric fans and brand new copper brass radiator.
Im going to check timing but I think it's around 12° btdc which should give me around 36°@ 3000. No pinging, not that I could tell. Spark plugs are autolite AR73 race plugs straight from the box into the motor, moroso super 40 wires.
Im gonna pull plugs and check them and reset timing and brake out vacuum gauge to tune the carb. Also clean up the carb and distributor some.
The last time I did this little maintenance routine truck ran b****'n so maybe thatll fix what ever it is I'm experiencing.