Cohort Outtake: 1954 GMC 620 Truck – Make Room for the Really Big GMC Six

(first posted 5/7/2017)     We’ve had plenty of love here for the Chevrolet and GMC “Advanced Design” (1948-1955)  pickups and trucks, but we’ve never properly worshiped this particular long-nose version of the medium-duty GMC, with its free-standing fenders and protruding front end, like this Model 620 stakebed shot and posted at the Cohort by tbm3fan. In case you’re wondering why it has that longer front end, it’s to make room for the biggest GMC straight six gas engine ever, the “360” and “426”.

The 400 and 620 series trucks covered the wide range called “medium duty”, for operators wanting something less than a full-blown HD truck, but still able to haul quite heavy loads, up to 32,000 GVW, and 50,000 GCV (with trailer).

The legendary “Army Workhorse” ohv gas six had proven itself in WW2 in countless military trucks and vehicles, and was a staple of the GMC truck line. It was available in the 400 series in 248 and 270 size, although starting in 1952, the ultimate 302 cu.on version was also available.

But for the higher speeds and heavier loads increasingly called for in the post-war era, GMC also developed a larger line of six cylinder gas engines, and that required more room under the hood. The two versions available in the 620 series were the “360”, with 360.8 and 155 gross hp, and the “426”, with 177 gross hp. There was also a 503 version available either later, or in the even larger HD models (900 series).


This one sports a “2TON 52” tag; that would make it at the low end of the weight range available, although those “ton” ratings were always a bit vague.


Not the sharpest picture of the interior, and for that matter, it’s not really all that different from a pickup, except for the five speed Clark transmission.


Sure is a fine looking truck, and the moan of that big Jimmy six working a load is undoubtedly a treat for the ears. We’ll just have to use our imaginations.