My dad always used to tell me to buy a truck that's already done, because you can't build it for the same price... I wish I had listenned to him...
Depending on where you are, you should be able to get a 89-91 blazer stock for between $500 (Pile of rust, but running -or- good body not running) to $2000 for a very nice stock rig. If you wantt o buy one with all the bells and whistles that you were going to put on it anyway, you are looking at between $4000 and the cost of a late model used car...
When you are looking at Blazers, make sure you get underneath and check the area in front of the rear wheel wells... they are notorious for rotting and causing a full body cancer. Same for the rocker panels due to the front wheels throwing mud at them all the time. Make sure the floor is solid, and make sure you hear it and see it run and drive before you even think about buying it... there's nothing worse than finding out after you bought it that the rear end was bad or that someone put sawdust in the tranny so it would shift for you while it was for sale... granted, that did NOT happen to me, but I've heard of it happening to others... Most importantly, if you are buying an air conditioned rig, make sure the system is charged and working... it's HELL to replace the A/C system in these trucks because of freon laws...
As for the rest of the truck, check the oil, tranny fluid, coolant level, and make sure 4wd works in low and hi.... when I bought my Blazer, the stick didn't want to stay in 4HI, and while it was a simple fix, it should have been a cue for me to walk away... Basically, if you are looking at a truck and saying "This isn't bad, $1000 worth of work and it should be good as new" then you should be walking away... $1000 turns into $4000 really fast.
Blazers and Jimmys are wonderfully awesome trucks... I wouldn't give mine up unless someone handed me a bigger one, or one with a diesel in it already. They can go anywhere the little trucks can for the most part, and in many cases can go further than the little ones... They are prone to wear and tear, but you must expect that when you buy a 20ish year old truck. The 305s are crap motors, the 400s in 1980 and before are decent but only 2 bolt mains, and the 350s are what everyone rebuilds into strokers or 355s. The 6.2 diesel will get you the best mileage, but seems a bit underpowered to me. Finding a Blazer with a Cummins swap already done with Dana 60 front and 14bFF rear will net you the best deal in my opinion... like I said, you can never build a truck for what you can buy it for.
