47-55.1 50 GMC 1 ton to 1/2 ton conversion??

[68c10owner]

I found a 50 GMC local for a good price. Only issue is it's a 1 ton and I've been looking for a 1/2 ton. The front fenders and sheet metal looks the same on this one but are the frames themselves similar? Can I remove the original 1 ton suspension and add a Mustang II crossmember? I could look for a different chassis but I don't mind doing the work if I can repurpose the original.

[dsraven]

welcome to the forum.
does your truck have single or dual rear wheels
mr48 is gonna be your 47-55.1 expert.
have you done any research on the independent front suspension models and manufacturers, their starter packages and their upgrade packages?coils or air bag springs, size of brake rotors, brake upgrades and how they affect wheel sizes that can be used, control arm tubing size and wall thickness, ball joint style and quality, tie rod end quality, power steering upgrades, cross member steel thickness, etc? there are some important things to consider when doing a comparison.
first I would recomend to put together a want list list and go from there. think about what you want the truck to look like and what purpose it will serve. like, will it be a lowered truck or do you like the stock height. what will you use for a drivetrain. what will the use be mostly, daily driver-high performance race use-show truck-etc.consider the track width of the IFS you choose and then think about how that will affect the style of wheels you can use-deep dish or not-and compare to your wish list
if you can, post up a few pics of your project. there is a "how to post pics" thread if you are unsure how to do that. we all love to see the pics and answer any questions you may have. there are some who may have parts you need, once you get started, but in order to advertise you probably need to join as a "paid member" or send private messages to those who may respond with "I have one of those"

[Ziegelsteinfaust]

The frame width's are the same, but the height and thickness will be different. Along with the kick ups or frame height taper being different. Which really doesn't matter.

They only made 1 cab and 2 different sets of fenders for the 1/2 to 2.5 ton I believe. I am not up on the bigger trucks.

My friend got a 1955 2 ton GMC with the 300 Jimmy 6 for $1000 for the engine initially. Since he wanted a 55 anyways. I convinced him to let me "fix" the truck for him. As I was going do most of the fab work anyways. Luckily he settled on a 1 ton suspension, duals in the rear, and a flat bed. But a Camaro clip or M2 set up would of been just as easy.

I sectioned the frame from 10 or so inches to 4-6. The frame was 5/16" thick roughly. Then slammed it as much as possible with a new straight axle for the front from a 90's HD 8 lug truck.

[studeclunker]

Well, I can understand why you don't want to drive a one-ton of that era. I have a '58 (top speed 45 mph) rides like a truck for some reason. Why don't you just frame it over to a comparable modern 1-ton frame? Or are you looking for all show and no work?

[mr48chev]

I'm not the expert I just know how and where to find the info. 51 years of working on them doesn't hurt though.

There isn't a lot of specific info on GMC trucks but all 1/2, 3/4 and 1 tons have the same front sheet metal outside of year specific changes. A conventional cab is a conventional cab and the only difference is the 1-1/2 ton and larger often have more holes in the firewalls for plumbing for Air shift for the 2 speed rear axle or other items that little trucks don't have.

All of the conventional cab trucks have the centerline of the front axle 17-3/4 from the flat of the firewall. 1 ton springs are 2 inches longer and a quarter inch wider than 1/2 or 3/4 ton springs. I am thinking that most of that length is in front of the axle though and that messes with the Measure from the center of the front spring bolt in the frame 18-1/8 inches to the axle center line. You will have to figure out exactly where the center lines and mark it on the frame and have notes and drawings with your reference points. Frame measurements so you can compensate for the difference will have to be dug up but if I get the nose off my 48 quick enough I can provide those with photos and drawings.

I haven't decided if I am going MII or Jag XJ on mine It may be Jag though. as I have one that is pretty well trimmed to be fitted up to my frame.

The rear of the 1 ton frame is Pretty much straight and flat and if you lower the rear much you will need to put a C notch in the frame. As far as setting up the rear suspension the good is that the frame rails are straight from the cab all the way back Making it simple to do spring or suspension swaps.