what steering box will work?

Per my last note, my 1991 Z71 requires a new steering box (badly). What model and year boxes will interchange? did they use the same box way into
the 90's, or was it something very specific for a few years? the truck is a 4x4, with automatic and 305 engine if that matters....any advice is appreciated!! A new one is BIG bucks, so I'd like to get one from the wrecker off a later model truck with low miles if possible...
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