After searching high and low for a short frame and finding nothing I'm looking to shorten my 8 ft original frame. I have overall dimensions but not sure exactly where and how to cut and reweld. Anyone have suggestions maybe even step by step with pics????

 

An episode of trucks did this with a 65 chevy. You may be able to find it on dvd or the internet.

 

i believe in that episode they chopped a section out of the frame beneath the cab. im not sure why. pretty sure you would have to move rear cab mounts and possibly crossmembers and possibly drill new holes to mount the bed. unless it was the only straight flat section of frame they had to work with. IIRC the bed portion of these frames is raised above the axle and the box supports under the floor of the bed are different sizes so the box sits flat on the frame. i have never done this on this truck or any other so you will have to measure your frame and decide where the best place to section it is. They made a Z cut about a foot long i believe in the frame to splice it back together. (cut down halfway through frame, back 1 ft, and down the rest of the way) '---, (rough idea) i have also heard of making a V cut although i think the Z cut would be stronger. ___>>____ either way make sure everything is square and level and get a good weld on it. then put a fish plate at least on the inside to completely cover the splice to add strength and keep the weld from cracking. good luck

 

I have a 77 with a n 8' box. I was going to put a shortbed on it and changed my mind.
Here's the dimensions...
6' and 8' beds are identical behind the wheels. the difference is between the front of the bed and the wheel well. a shortbed is actually about 6.5 feet and to put the shortbed on I would have to take either 16" or 17" out from the frame between the back of the cab and the front (rear axle) spring mounts.

I was also thinking about maybe leaving enough room for a set of stacks or just leaving the frame long and getting an aluminum fuel tank made to fit between the cab and bed with stacks either side

You cut the frame square with a cut-off wheel in a grinder.
Bevel the cuts inside and out leaving 1/2 the thickness of the frame's metal un beveled.
Butt it together then weld it both sides
Make a square fishplate and camp it centered over the weld inside the frame with points vertical and horizontal as a diamond.
It should sized so that it is about an inch from the top and bottom stringer of the frame channel
Weld it in around it's perimeter
cut a section of the frame you removed to plate over the outer rail bottom
it should be L shaped, extend halfway up the frame channel.
It should extend front and back 1/2 the frame channel's height from the weld then taper at a 45 degree angle to the bottom web.
This plate is bolted in from the sides but NOT into the top or bottom web.
If you do weld it, you weld it in using plug welds. YOU DO NOT PERIMETER WELD THIS PLATE.
Most of the frames strength is in the top and bottom stringer and the stringers width into the web of the frame. drilling or welding into the stringer significantly weakens it but a hole with a bolt nut and 2 washers torqued down in the hole restres 85% of the strenth lost by drilling the hole
Welding in the stringer hardens it making it brittle and crack prone.

It's been done other ways but this is the way to do it according to the automotive engineers for maximum service. It is the approved method for shortening or stretching commercial truck frames which are made from high tensile steel

 

Torch,

I agree with almost everything you say.

except... At my shop when shortening a commercial frame we allways move the axle forward rather than chopping out the frame. But welding on the end of the frame for a couple foot extension is fine.

If we were to do a shorten in the middle of the chassis(behind cab) we would do a step notch rather than butt the chassis up flat. Make sure to bevel all areas to be welded.

just my 2 cents...