wheel bolt pattern? The stock split rims are cool but this thing needs new rubber asap.
Since the rear is a full float axle, my guess is going to be it's a 3/4 ton truck. Since you didn't post up a picture of the wheels, I am going to guess they are 6 lug? If so, the pattern is 6 on 7.25". They are near impossible to find in a non-split rim pattern as it appears only IH and old dodge powerwagons used that pattern. As you can imagine brake drums are also going to be hard to find. Chances are you can come by them used, but I don't know if you'd be able to find new drums if you needed them. Last I heard people with the 6 on 7.25" lug pattern were getting wheel custom made to get rid of the split rims, but I think the shop people preferred went out of business.
diffs/springs/lift? These appear very similar to GM parts, what are some good swaps?
They are not GM, chances are they are Dana with the exception of the rear, which May be a Dana or a IH corporate axle. The Dana axles IH used are just like the Dana axles every other manufacture's used. You're truck should have a Dana 44 closed knuckle front, and either an ra-15 IH rear or a Dana 60 full float. The IH axle looks similar to, but larger then a 9" with the center section dropping out of the front. There are no "lift kits" available off the shelf for the trucks, but if someone wanted too, you could piece one together by rebuilding the suspension, or getting custom leaves made. I know Jeff (the owner of IH parts American and operator of this site) is working on a d-series lift kit. The d-series of truck is one generation newer then your truck, but the leaf packs maybe the same or similar.
all wheel drive- are these things full time all wheel drive or selectable all wheel drive?
All wheel drive in this instance mean selectable four wheel driver. It is not full time, and it should have an np-202 transfer case. The options should be 2 high, just driving the rear tires, 4 high, driving the front and rear axles with the hub locked in, but no additional reduction from the transfer case and 4 low, same as 4 high, but reduction added by putting the transfer case in low gear.
Good luck