On those spindles make sure you aren't looking at S10 Blazer parts. In 98 the Blazer started using a different spindle than the 2wd pickups.
On bigger tires be careful when using anything but stock wheels because off set and backspacing on aftermarket wheels is all over the map and will cause more rubbing problems than the tires. With 2wd stick to 0 offset wheels.
If you have 2.8, 31 inch tires will feel like you are dragging an anchor. If it's a 4.3 it'll just feel gutless. If it's a Tutu, forget those big tires.
The lift spindles for the 98 Blazer are made out of unobtainium. Actually they may be made of dontexistanium. I can't say I've ever seen any. I was considering lifting my truck another 2 inches and putting 30" tires on it, but the fact is (at least to me), the truck's track and that height aren't a good combo for handling and probably outright dangerous like that. 235/75 is plenty big. So I opted for Blazer spindles on the front cause the brakes suck.
And you're right on about the tires too. My 91 with a 2.8 had like 215/75/15 on it one time. It couldn't make it up hill on the interstate in 5th. Terrible. I could only imagine what 30" tires on that turd would have been like. My current truck, the 84, with the EFI 3.4 and 3.42 gears, does pretty good with the 235/75/15 on it, but you can tell it certainly stole a lot of power from the truck vs when it had the 215/60/15 on it (too small I know). You could get it sideways pretty easy flooring it easy coming out of a turn, so for daily driving it's actually more civilized with the big tires. Stock? No way. That thing with the 2.8 and the stock carb? That would have been pathetic as ****... I bet it couldn't have managed 60mph on the interstate. What a turd that truck was with the 2SE.