I went craigslisting...check it out.

[83GMCK2500]

DISCLAIMER: None of these are mine or anyone I know, just got bored, found 'em, sharing 'em.

78 gmc 3/4 ton - $4000 (west valley)
1974 GMC the beast - $2000 (wenatchee)
74 gmc (Rd 68 )
1976 GMC short box - $1800 (Pasco)
Flatbed Truck - 1974 GMC - $1000 (Maple Valley)
'78 gmc sierra - $4000 (port orchard)
78 GMC crew cab 4x4 1 ton (Spanaway)
1976 gmc-1360-283-5509 - $1500 (oak habor wa.)
handy man special - $2300 (camano island)
1978 GMC 1/2T SWB 4X4 lifted - $3200 (Vancouver, WA)
1975 GMC 1/2 ton 4x4 project $1500 obo - $1500 (Damascus OR)
PARTING GMC 1978 (VANC WASH)
1976 GMC 3500 - Dually - 454 Big Block - $1500 (Forest Grove)
1979 Gmc sierra grande lifted - $2400 (gresham Or)
GMC Sierra classic 400 - $4500 (Hillsboro)
1978 GMC 1 ton work truck - $900 (Spokane Valley)
78' Chevy/Chevrolet/GMC Chopped PU - $3500 (Elk,WA)
1978 GMC 4 door 3+3 - $1200 (lynden)
1978 GMC 1/2 2wd - $1150 (Scio)
77GMC Lifted 4x4 ShortBox Trade - $7500 (Please Read Ad)
1976 GMC Sierra Grande 4WD - $4200 (Woodburn)
1975 built and lifted GMC - $4000 (salem)
1978 GMC 3/4 ton W/Camper price reduced OBO - $2000 (ne portland)
perfect mudder - $250
reliable work truck!! Great offer - $800 (keizer & surrounding)
Chevy truck/blazer grills - $5 (albany)
1977 GMC Sierra C10 - $5250 (Redmond)
1974 yellow GMC - $3000 (prineville Or)
1978 gmc blazer - $1800 (Prineville )
1977 GMC short Narow Box to Trade (Albany) (HOLY TAIL LIGHTS, BATMAN!!!)
1973 GMC Jimmy 4WD. - $2000
GMC classic - $3995 (Myrtle Point) (oh, sexy tailgate)
1977 GMC 3/4 2WD - $1995 (SPRINGFIELD)
1977 GMC 2 wheel drive short wide - $3650 (florence)
1977 GMC 3/4 ton 4x4 Pickup - $4000 (Marcola) (mmm, tach)
1974 Jimmy K5 Blazer - $2800 (Springfield)
1975 GMC BEAU JAMES Serra Classic - $19995 (Richland) (oh my...oh Lordy, my pants might've just got tight...)
1978 GMC High Sierra - $3000 (Polson, MT)
75 gmc - $1500 (Charlo)
1974 2wd 2500 gmc 350 auto v8 - $995 (arlee)
1978 GMC Sierra Classic Truck 4x4 - $1300 (Eagle)
1976 GMC vandura 4×4 - $5000 (meridian) (probably the only G-Van I'll post...)
shortbox chevy project (west boise)
1978 GMC Sierra Grande 15 - $5995 (Garden City)
1977 GMC 4x4 3/4 Ton - $500 (Meridian)
1978 GMC 4X4 pickup - $850 (klamath falls)
77 GMC pick up 320 HP - $2995 (Nampa)
1975 Chevy C30 Dually Custom Hauler - $25000 (Caldwell)
1976 GMC Short bed - $3500 (Medford)
1977 GMC dually one ton - $1000 (white city)
3/4 ton GMC sierra grande 1978 heavy duty 4WD - $1200 (Shady Cove )
gmc 4x4 - $1000 (Eagle point)
GMC TRUCK - $900 (S. OREGON)
1970's 1980's GMC Chevy Truck SHORT BED box - $125 (Sunny Valley / Wolf Creek) (BIG 10 bed)
1973 gmc step side 2wheel drive - $3500
1976 GMC 2500 Plow Truck $3,800 - Lewistown
TWO 4 ONE - $2000 (Kalispell)
1976 GMC Truck - $2500 (susanville)
1977 gmc sierra 2500 - $1000 (arcata)
1978 GMC Sierra 2500 - $4500 (Chester, Id)
1976 GMC Lifted 4x4 - $3000 (Rigby)
1977 gmc $3,500
1977 GMC 3/4 TON 4WD PICKUP - $3995 (POCATELLO, IDAHO)
Hot rodders must see!!! (carlin nv) Interesting...427? All original...yeah, riiight.
>>>> TRADE 4x4 <<<<< - $4000 (chico)
http://chico.craigslist.org/cto/4112270793.html
1973 GMC grille - $25 (Gardnerville)
74 GMC HIGH SIERRA FOR SALE OR TRADE - $4000 (SUSANVILLE)
1976 GMC SIERRA CLASSIC 4X4 K2500 - $3500 (A****er)
1975 GMC Suburban Sierra Grande Pre-Smog Mint Green - $5500 (Auburn, CA)
75 gmc jimmy/ blazer convertable - $1500 (Colefax)
1976 GMC 3/4 ton camper special
1977 GMC Flatbed pickup**Custom Bed NEW TIRES/RIMS - $3400 (olivehurst)

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Ok back to my homework, but there are all of the GMCs from 1973-1980 within about 500 miles of me on craigslist that have pictures posted.