3&6 missing, stalling when put in gear

This is not a dwell issue. This is an issue with 3 and 6 only. Dwell affects all 6.
Here's what I would do, since you don't want to do the cylinder balance test. I would swap the wire from #6 to another cylinder, and see if the problem follows the wire. I would do the same for #3. If no change, I would swap the plugs to different holes, also to see if the problem follows the plugs. You see, the timing lite is telling you that those two cylinders are not firing correctly. Whether its a plug or a wire or faulty A/F charge, you have to find it by process of elimination. The easiest to prove is the ignition system.
So if swapping the plugs and wires around makes no difference, then you have proven the ignition system is not the source of the issue.
Next would be the fuel system.Since it runs on the other cylinders, just fine, the carb is fine( it cannot tell one cylinder from another); so that just leaves the intake manifold and the connection of it to the head. Since you say you cannot find a vacuum leak,you have sorta proven that system is ok.
That just leaves a mechanical issue. But you have proven the compression is ok and the valve clearance is, at the very least, not too tight. So, what you are saying is the engine is junk.
-But hey, there are still several things to prove. #1 is valve-action; both valves in both questionable cylinders must be proven to be fully opening, and fully closing, and doing it at the right time, and reliably. You see, full compression does not prove that the cam lobes are all there or that the valve springs are not broken or that they have sufficient pressure to do their jobs. So that would be the next place to look.

But back up the busaminit.
You say you could not find a vacuum leak. I just want to throw this out there.Suppose the intake was cracked in the area between it and the exhaust manifold,where they are bolted together? If the engine was sucking exhaust there it would run kinda crappy.And you wouldn't find it in the normal way of checking. Whether or not it would affect just two cylinders, I cannot say. Nor can I figure out how or why the timing lite would see it as it now does. So this would be just something to keep in the back of your mind, if you cannot find the issue in the valve-action.

I also find it perplexing, that the only thing that 3 and 6 have in common is that they fire one after the other, leading a guy straight to the distributor cap; and that the cap is new.Hmmmmmmmmmmmm