Aggravation...grrrrr

Alright, here we go (sigh)
1986 Power Ram 2500 (W250) 4 wheel drive.
360 4 bbl 435 4 spd NP208 transfer case.
Purchased about a year ago. Ran fine no major problems except for a cracked exhaust manifold.
About 7 months ago, its started running flat. Sounded and felt like a carb issue.
Rebuilt the Rochester quad, found one of the tubes had dropped, put it back together, with tube stuck back in place.
Ran fine for one day, and started screwing up again.
Bout 6 months ago, lost my license, so didnt really drive it much since then, except for moving.
Just got license back(and I really want to be playing on in and around with my truck), and the trouble still persists.
this is what its doing.
It will run fine while sitting, idles alright, revs up so so.
Put a load on it, and it sputters, backfires, chugs, pisses, snorts, bitches and moans. If I get to 55 on a flat, it takes about 5 miles, lurching and wheezing all the way.
Really Bad.
I tried swapping another Carb on, no luck, just as bad, but with more power behind all of it, lol.
The second carb is kinda(holley 600 4150) iffy, Im waiting for one of my Edlebrocks to make its way home, so I can start with a known good carb.
Other things that have crossed my mind of course, is timing, etc.
I timed it the other day, using a timing light.
Pulled the advance line, and it sat at a steady 7-8 before (dirty marks, kinda hard to see).
Flat steady, no fluctuation, no wobble, no waver.
Rev it up, let it off, and it drops down and stays steady.
That should preclude a loose timing chain, or bad distributor drive, or intermediate drive or cam gear, etc.
Next things I could guess would be Cap, rotor, wires, plugs, coil and vacuum advance module. etc.
Im going to try to pick u an ignition module, ballast resistor and the spark advance module(whatever it is, (Im far more familiar with 70s dodges) I have two module boxes on the fire wall, plus a 4 prong ballast resistor.
Then theres the intake gasket, Im pretty sure thats alright, but Im going to check it out anyway. Like I indicated, it ran really well for the first several months, and not to bad on gas, either.
Ive ruled out head gaskets, unless its a cylinder to cylinder, or oil passage to cylinder leak.
The waters green, with no oil slick, and the oils oil, with no frothing, bubbles or residue in it.
This last weekend, I performed successful surgery in eliminating and re-routing some of the ex emissions stuff. Some of it was dead anyway (smog pumps, etc.) and the rest was the charcoal canister. I left the vapor canister though, not sure how to elminate that safely yet.
The truck seemed to run a bit better, for awhile, but no major improvement.
Im still learning all the obnoxious stuff thats included on the 86 trucks, so Im sorta at a loss here.
Ive heard theres some sort of module under the dash, that uses a 9 volt battery?
Like I said, Im not real familiar with the electrical and emissions on this truck yet, so is that a nasty rumor, or something that could effect the truck this way?
I mean my 73 was easy, emissions..eerrmm, PCV valve, and breather cap.
All the "elecronics" were trouble shootable with a multi meter and test light.
A handful of fuses, a couple rolls of wire and a box of connectors would fix anything on it.
All the mechanical took was the ability to read specs and measuring devices, and a good set of wrenches.
I admit that for all the stuff that comes easy, emissions routing and the newer electrical crap stumps me a bit(to many relays and weird little boxes).
I used to have a killer trouble shooting manual, covered everything from generators to building fusible links, fuel systems, brakes and everything else and so on (got stolen), and Ive forgotten so much of the stuff that I knew in regards to that it pisses me off.
Second problem I have, (I think Ive figured this one out) is not constantly, but about 2 out of 3 times, when I start it, I have a "clunk" when the starters cranking. The starters tight, so its not shifting around. Related to this, I believe, is a occasional nasty vibration around 55 or so, and occasional funny noises when I clutch to shift.
Im guessing its a loose flywheel, or hopefully (for sake of ease) loose friction disc/clutch housing.
any and all suggestions and hints would really be appreciated..I want to drive my freakin truck ! ! ! !
Thanks.

Seeing your timing mark move w/ the vacuum advance unplugged means your mechanical advance is working, but the vacuum advance chamber could be bad. Take a small hand-held vacuum pump and apply vacuum to the chamber and observe the "little arm" that comes off the chamber and into the disributor....it should move in. If it doesn't, you need to replace the vacuum advance.

Clunk noise could be a cracked flywheel or a few bad teeth.

yeah..I forgot to mention that in the list of stuff...lol
I did test it, though (old fashioned method) by sucking on the line to the vacuum advance, and allowing it to "hold" the tip of my tongue.
Im going to replace it, anyway.
Cause thats just a general quick check (dont have a vacuum pump).
So first, Im going to pull all the plugs, regap clean and re-install em.
then yank the cap and rotor, ohm the ignition wires and install a new coil as well.
Im guessing Ive got a combination problem here, since I dont think the truck got a lot of routine maintenance before I got it, and moneys been tighter than...well, you know.
so I havent exactly been able to go through all the stuff Id normally do, either.