Depends on the engine. 305s and 350s got injection back in the mid 80s (TBI). I don't know when the 454 got it's first taste of electronic petrol management.
As for a bare-bones 'Burb, I'd keep an eye on utility company auctions. They tend to order units with lots of useful stuff but little in the way of other amenities. About ten years ago Dad got a Suburban from a phone company auction that is exactly what you wanted - 3/4 ton, 4x4, 350, A/C, auto tranny, manual transfer case, manual windows & locks, vynyl seats, and rubber floor mats. It had a billion miles on it, the paint was pretty faded, and the interior had obviously been rode hard, but mechanically it was sound and decently maintained. He still has it.
Brad