I doubt a 1980 LC has a vac retard distributor, but if so, remove and plug the 'retard' line. Put a slotted dummy cap over the dist port to keep mud wasps, dirt, etc. out of the hole.
If you have the later dist. with two ports (one for the main vac advance and one for the little extra bit of advance), be sure they're on correctly. Use a vacuum gauge and rev the engine to check that both ports are getting the correct vacuum. Put a hose on the dist. adv. port and suck on it to be sure the diaphrams aren't ruptured.
Your jetting may be too rich at higher elevations, but that is a separate issue from the vac advance setting. Many old FJs won't exactly go 65 around Dillon, so join the club in the slow lane. Blow the doors off an old VW Bus if you need to feel the power you have! ;-).