ive got an 83 3/4 ton 4wd. its 350 gas so i cant help ya with diesal. id love to diesal mine but its so far down the priorities list i can even see it happening. the engine only has about 19 thousand on a rebuild so its good for a while.
the tranny lost over drive pretty quick but that was an error on mine and my brothers part. we made a trip from houston area to eastern oklahoma and pulled back a tractor and implements, then almost immediately we made a run from there to san antonio area and brought back a heavier tractor.
we used over drive, not knowing you are not supposed to use it with a heavy load. from what folks are telling me, we ruined it.
this might be silly, but if the one you're looking at has the AC blower in the back, expect that fan to go out sometime. mine is squealing but still blowing for now.
a brother had an 83 like mine. he put in some kind of splitter and was pulling a heavy presidentual RV for years out west in the mountains.
there is SOOOOO much room inside those suburbans, its like you can build a house in the back!
i can say they are tough designs!
heres a pic of it on a 12 degree oklahoma morning.