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Mountain Man's K5 Extended Cab Flatbed Project

Turning a North Idaho rust hog with 33"s and blocks into an extended cab flatbed type thingy with 37"s and 3/4 or 1 ton axles. This will be fun.....


I recently acquired a 1975 K5 Blazer from a guy in town for $800. I did this because I know inevitably my current 4x4/Winter rig is going to have a catastrophic failure at the worst possible moment and that can kill you up here in North Idaho. It gets pretty cold up here and we currently have the title of being the most remote state in the lower 48, although I really think Montana is more remote. Either way, reliable transpo on highways and side roads with up to 18" of snow (the State/County plows are few and far in between) is pretty important to live an uninterrupted life up here from October/November to April.

My current 4x4 driver is a '94 Toyota 4Runner with taller coils and a mild body lift sitting on 33"s. The 4Runner has been a great reliable rig for 3 years now, but the mileage on the drivetrain (244k) has been concerning me. The 3VZE 3.0 V6 has never had a head lifted off of it to my knowledge and these engines are notorious for blown head gaskets by 100k miles. I did a timing belt at 220k, all new brakes/radiator/hoses/belts/plugs/front CV axles/HD coils/body lift when I bought it at 212k. The 4R had worn out 32x11.50 MTs on it when I bought it and was pretty slow with the stock gearing, its even worse with the 33x12.50 ATs retreads I put on it after the lift. The transmission doesn't like to shift past 3rd gear until it has been running for at least 15 minutes and every other time its driven on the Highway at 62MPH (50mph on the speedo) it likes to intermittently drop in and out of overdrive for no particular reason. I was toying with the idea of a Solid Axle Swap (SAS) along with a 5VZE (3.4 V6 in newer 4Rs) Engine/Transmission swap and converting to leaves front and rear/going to 35-37"s. After doing all the math, it looked like I'd end up spending $10K+ to do it right and frankly I don't really like the SUV body that much. I have had no backseat since the day after I bought it and the front passenger seat has been replaced with a HUGE plywood carpeted console that houses my ground bar and fuse block directly off the battery with 2 gauge cable to run my CB, 10 Meter radio, VHF, UHF, and 2 RF amplifiers which I'm not going to specify the bands they are being used on. The console also has a slick 6" wide compartment with a hinged lid for quick access to my plain jane M4 AR15 truck gun. In short, only me and my 100lb red lab "Mick" ride in the car and the SUV body is a big waste of interior space. I also have to smell the garbage when I make a run to the dump. I wasn't going to put that kind of money into a Rig that wasn't ideal, and I've worked on my fair share of K5s including a '54 F100 on a K5 frame. This paragraph pretty well explains the motivation for the K5 build.

At this time (6/30/2018), I've gotten the Blazer home and have taken the top off and made a few dump runs with it. The NP203 is in 4H lock because the front Ujoint on the front driveshaft broke and the previous owner decided it was easier to just lock the T-Case instead of fixing the driveshaft. I have removed the seats and carpet and lo and behold it has the same cab corner/floorboard rot that every Blazer that has ever seen salt has. I ordered everything I needed to fix the rotted panels from the front bumper to the back of the cab from LMC (lots of oversize $20 shipping charges). Then I decided that I was going to end up with an even bigger SUV if I just restored the Blazer and put the top back on, this is the opposite of what I wanted. I've got 5 days off next week and sparks are gonna fly.

The plan now is to basically take a K10 cab and cut it off behind the windshield and at the bottom rear corner, and use it to extend the Blazer cab back to where the factory wheel well starts. Depending on my mood at that particular moment, it may overlap the wheel well just a little bit. This will give me enough room behind the seats for my black rifles, tool boxes, speakers, and maybe a sandwich and some beer. The heat should be excellent in the winter time with less than half the cubic feet of cab to keep warm. The back half of the truck will ideally have a flat bed with a ramp tucked underneath that is grooved on one side and smooth on the other. This will allow me to put my 2000lb winch against the cab and pull dead deer/elk/cougar/moose up the smooth side, and run dirt bikes up the rough side. The ramp should be solid enough to use as a bed extension to hold up the rear wheel of said dirt bikes/whatever I happen to be hauling. The truck has 87k original miles and the 350 in it has an Edelbroc carb and manifold and runs strong. I was surprised to hear the 33"s chirp during the test drive when I opened up all 4 barrels from a stop sign. This guy has a lot more balls than my 4Runner. I'm assuming the axle gearing to be around 3.07 ish since it is only turning about 1800 rpm at 65 MPH according to the GPS. The stock turbo 350 transmission shifts nice and the kick down works just fine. Hopefully when I source the 3/4 or 1 ton axles I can go to 4.10s or so to compensate for the planned 37" tires. The blocks are coming out and the plan is to run 6" leaves with 2-3" of body lift. The back half will clear just fine, but I'd like to keep the fenders intact on the front if possible.


K5 Blazer
Trim Level
Factory Options
350/ eddy Manifold/Carb, Headers and Flowmasters dumping over the rear axle
Transfer Case
NP203-Either to be modified to part time or replaced with NP205
Stock-to be converted to high steer and box mount reinforced on frame
4" blocks- Going to 6" leaves.
Stock 1/2 ton-going to 3/4 or 1 Ton with 4.10s
Stock-going to whatever fits the 37"s I end up with
33" BFG AT-going to 37" Retread MTs
"restored" 20 years ago with metallic blue and failing miserably with road salt. Likely going to Flat OD green or Khaki.
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