All sound advice. My experience with fuel delivery probs (pumps, clogged filters, etc) is that you'd have a high RPM die off after a given amount of time at high RPM. Basically it cuts out hard when you burn through all the gas in the carb bowl and stalls for a few seconds before it catches up again. I've had more major problems in that area though, so a minor clog might be a bit less obvious, but I'd think winding it out in 2nd would show more of a problem than running 50 in 4th.
Sounds more like an ignition or vacuum thing to me. Points, coil, coil wire, weak plug on one or more cylinders, dirt/crud in cap causing bridges or shorts. Plug off all the vac lines you can find to check though, especially the air cleaner stuff like the flapper for the hot air intake. Make sure you label as you go though.
Another thing that jumped into my head was if you happen to still have a catalytic converter on it, it may be plugged up. Usually this is a high RPM thing no matter what gear you're in, and it has symptoms like hot smells and such from what I've heard. My 86 trooper is the first thing I've owned that had one on it and it hasn't plugged so I don't know first hand what you'd be dealing with.
This time of year for some of us is water in the gas time too. Just another thought.