6' 2", so not as tall as some of my brothers-in-OD-iron.
I upgraded from box to spring-base, then swapped the stock seat assemblies for a set of more modern contoured .mil seats. I've no idea what they came out of, as some had front/back adjustment, some didn't, different bolt patterns, etc. Some time with a drill was needed to get them to fit on the spring bases.
Without a tubular frame & with thinner cushions, I gained quite a bit of legroom & windshield visibility. Much more comfortable padding than stock seats, definitely appreciated on longer trips. Contoured padding supports better across the your body, instead of just at the pressure points. Combining that with better quality foam allows even thinner padding than you'd think would be comfortable.
The adjustment on deuce spring bases just tweaks spring-tension, not quite the same as ride height. Mine's set to keep me from swaying too much, rather than for height. You'd need to tweak the geometry of the spring mechanism to get major adjustments in height without de-tensioning the spring so far that you bottom out the seat on every bump. Supposedly, air-ride bases are an option, but you might want to do some research before you buy anything.