lol i couldn't resist... i would keep the whole front axle assembly, the d28? doesn't always last that long, would be nice to have a replacement... check the gears on your new one, if they are different, keep your rear carrier too, incase if the front grenades it takes out your front gears, that way you don't have a truck with 3.55's and a replacement 3.73 or something, because that won't work (your new truck will still have 3.55 and your replacement will have 3.73)... actually, keeping the rear diff wouldn't be a bad idea either... tc would be a good idea... trans i think are fairly cheap and easy, plus yours has a blown clutch and is manual, an auto to manual conversion is a little work... i would check what kind of tc you have in your current one... if you keep the rear carrier make sure you keep the pinion gear to go with it... it's useless without it...
i don't know what electronics come on your 88, but i would keep the maf, tps, and any other small relatively expensive sensors that tend to go out... i priced out a maf for my 89 at hallmark ford, they wanted like 350 for it i think... so i would keep yours, if equiped... tps's are cheap, but they are small, easy to store, and often wear out...
i would keep the airfilter box too, just for future mods if you wanted to snorkel it or something (like mine, i wish i had a second box for when i did mine, i drove around with an airfilter taped to the top half for a few days while waiting for glue to dry...
shift knobs, ALWAYS keep your shift knobs, i like to collect my old vehicle's shift knobs (even though i don't have any of my old ones any more, they are MIA... i think i just lost my bII's though... my mustang's is still on the shifter...
UMMMMMMMM... front drive shaft, although i have a feeling it might be a different length because of the auto/manual, but i don't remember for sure... i know ford trucks had problems with the head light switches melting in the early to mid 90's don't know if your truck will be in that year range and have susceptible switches, so that's something you might want to grab... dash clusters tend to fetch a few bucks for some reason... fuses i usually pull, just because you can never have too many good fuses kicking around, and they are free... used to come home from jy's with pocket fulls of fuses...