I think a K5 Blazer makes an excellent platform for an expedition rig! They're cheap, plentiful, easy to find parts for, cheap to buy parts for, and easy to fix!!! I had an 87 Jimmy (that I never should have gotten rid of), I've been trying to load pics for about half an hour now but can't get them to work. I'll try again later. It was pretty much 90% build as a rockcrawler but, could have done expeditions fine with a few tweaks. Specs:
GM replacement engine 350 TBI
sm465 completely rebuilt (by Novak, IIRC) with ORD short shaft 32 spline output
ORD triple stick 203/205 doubler with short adapter, 32 spline in and both outs (Ford 32 spline front output), up clocked (about 117:1 crawl ratio)
^ completely custom box crossmembered 1/4" steel skidplated belly pan to mount and protect the doubler
1410 u-joints on HAD driveshafts (except rear at t-case, had the HAD t-case mounted disc e-brake so, had a beefy CV joint there)
Front axle: Dana 60, 4.56 gears, ARB diff, Solid cover, 35 spline outers with spicer 806-X u-joints and Dynatrac Dynaloc hubs
Rear axle: 14 BFF (CUCV rear), 4.56 gears, Detroit locker, disc conversion, Solid cover, Ruffstuff perches (allowed moving axle 1.5" rearward from stock)
ORD crossover steering, ORD steering box frame repair plate, ORD steering box reinforcement, and PSC hydro assist setup
front suspension: 3" Tuff country EZ rides with ORD greaseable shackles, ditched the swaybar (couldn't fit with crossover steering and 3" lift) Daystar extended bumpstops, Bilstein 5100 shocks on superduty towers
rear suspension: stock rear springs, ORD shackle flip, custom frame crosmember to inboard mount Bistein 5100 shocks (RS perches moved axle back a little to compensate for the amount it moves forward with a shackle flip)
Wheels: H2 takeoffs (with 1.5" spacers, on the rear axle only- to match front and rear track width)
Tires: 37" Cooper STT muds (very good tires!) didn't have to do much cutting to fit them at full stuff and full turn
ORD front bumper with Warn 9500TI winch and Baja Design Soltek lights
DPI rocksliders and rear bumper (with PIAA backup lights in the rear bumper, they worked great!)
I don't even know what I had in it, likely $30k, I sold it for $5000, that was the biggest mistake I've ever made!!!! It's on its second owner since me, some offroad racer in Sweden owns it now! Totally wish I still had this truck!!!!!!!!!!