I converted my 88 tbi 4x4 from a 700r4 to a th350, I had the kit from tci or tecpak fittzall or whatever, short shaft and a spacer that was like 1.xx thick, bolted right up in place, I had NO driveshaft length mods, NO crossmember mods or movement, just all right in place.
My shift linkage bolted up and everything, you must run you a vac. line to the 350 modulator, not a big deal though, and then when your in dash indicator(if it works) will say it's in od when it's actually in d. It will also not shift down into 1st because 2nd will be 1st. Nothing is that big of a deal though. we drive mine on the street, hauling, unloaded, highway everything, has good power and plenty of grunt and I just have a stock 350 rebuilt with tbi and run 3.42's out back and up front with 33's on it now.
It ran great, but now I got hiccups with the tbi setup so soon it's gonna be carb'd.