From wiki(not entirely accurate at times), it appears that Suburbans got diesels from 81 to 97(plus more but those are my focus). Granted, 78 to 81 is that great LF9 350 one and 82-91 being the 6.2L detroit.
FWIW, I like the interiors of the older rigs(simple, non-add on meth design). Hell, I use 86 S10 truck/blazer steering columns in my FJ55s
A seat/bench issue is as 'simple' as fabbing a bracket for new seats.
I like the older 6th gen (67-72) body style except for the three door ;) A close 2nd for me is the 7th gen(73-91) Not 'keen' on 8th gen(92+) but I would suck it up and deal with it.