You'll want to look for a tranny and transfer case combo that have their shift levers in the same configuration as yours. Some transfer cases are forward shifted and some are top shifted. I have an R151F and matching transfer case, the turbo setup, which is forward shifted. That's probably what you have. Get it right and you won't have to cut up your floorboards to fit the other configuration (top shifted transfer case).

I had an '84 extra cab, with the G series transmission, that was also a forward shift set up. However, the G series is not considered to be as durable as a W series transmission. If I'm recalling this correctly, the W series from the mid-to-late 80s is mated to a top shifted transfer case. I think you want to look at 90s models where forward shifted transfer cases were used.

Do some searching on the marlincrawler.com website. They have great sections over there devoted to transfer cases and transmissions. Tons of golden information.