Sounds like a nice truck man. My advice would be - f you really want a smooth ride out of a chevy truck from '73 - '87, dont buy one! of course there are things to do to fix your brick-mobile ,though, dont get me wrong. If you enjoy mudboggin and if you do it often and are going to need the clearance, then keep the blocks, they affect nothing as far as ride quality. If you want it a little lower, find a 2 or 3 inch lift block and replace those 5 inch beasts. You'll have to get a reply from someone else about your leaf spring problems, i'm not too much of a pro at that stuff, sorry. I think you might be best off turning 33s with gears over 4.00, but, do what you want, like you said, if you cant go 55 as you are now, you might consider changing your gears, but c'on its a big ole mudbogger truck nobody expects it to keep up with a ferrari or anything!
Good Luck!
Hope i remotely enlightened you on what you should do!