So.... time for another update... it was probably 5 or 6 weeks ago I started banging my head against the wall... van wouldn't run right... backfiring through carb. Checking carb, fuel filter, timing, etc. Finally found loose nuts on exhaust lifters rockers. Changed those out. Got better... somewhat. Van would die if you slammed the throttle, or put it under too much load.(power brake). Rechecked timing, rocker arms, carb. Nothing. Changed carb with a known good one. No change. Checked compression. Good. Vacuum. Behaving normally for 7000 ft. Vacuum leaks. None. Changed plugs again. No different. Last night I was talking with a buddy about our respective builds (he is building a drag S-10), and he said something about his ignition system. Dawned on both of us, old cap, rotor and coil. GM HE I. He told me to try the spare that came off his truck. Went out after work this morning and swapped back to my original carb, and put it on. Like night and day. Still need to undo the carb and timing tweaks from the fiddling, but it's frigging cold and we are supposed to get snowmageddon this Thanksgiving weekend. Possibly this afternoon.... such a relief.