Would I need to fish plate both sides of both pieces? I was thinking since one is nested tight inside of the other that I could fish plate the inside and out side. Making a plate 1 for each of the rails. I am surprised that some one else has not done this.

 

I think I understand what you are saying Chuck, by staggering your cuts in the 2 layers of frames then sliding them together so the welds are equal distances apart? That's my understanding and the way I would do it.

 

Exactly what I was thinking then plate inside and out side. Would that be strong enough?

 

That would be plenty strong enough and the strongest part of the frame I would think.

 

That's what I was thinking....

 

Cutting the outside layer will be the easiest, the inside corners will give you the most trouble.

 

Besides a good grinder with a small wheel what would be the easiest to cut with?

 

My best friend has been a grinder with those zip blades, for the tight spots I use a die grinder with the same type blade. If you happen to cut into the other frame section a bit I don't think it should be that big of a deal unless you broke through, save you smallest wheels to get tight in the corners. It's going to take some time. There are likely some on here to give you better guidance for making the cuts than I but I generally find away to get what I want to accomplish.

 

For a 10' bed you will need approximately a 145" wheel base to look right. The 134" WB trucks had a 9' bed and the 158" WB used a 12' bed. I would cut the out side frame with an angle grinder and a 1/16" cutting wheel on about a 30 degree angle. Cut it in the same place on both sides, being careful not to cut into the inner frame. Drill the rivets out of the crossmembers between the cut and the front spring hanger on the rear axle, next drill the rivets out of the front spring hanger on the rear axle. I usually drill a 1/4"-5/16" hole thru the rivet then use a larger drill to remove the rivet head, then drive the rivets out. Once the rivets are out, you should be able to slide the outer frame and rear axle off of the inner frame. Once you have it apart, cut the outer frame to length at the same angle you cut previously, bevel the outside only so you can weld all the way thru the outer frame. The inner frame will need to be cut to length and also you will need to cut a wedge out of the lower side to match the taper on the piece you cut off. Bend the bottom flange up and weld the bottom corner. Once the inner frame is modified to match the piece cut off, slide the frame back together and weld the cut. If welded properly, there is no need for any fishplates. The weld can be ground smooth and you won't even be able to tell it was cut. Drill the rear spring hanger rivet holes and the crossmember rivet holes thru the inner frame and bolt everything back together with grade 8 fine thread bolts. On the spring hanger, you may have to drill or ream the rivet holes for a tight fit on the bolts. Use a bolt with an unthreaded shank that is almost as long as the thickness of the frame and spring hanger combined. I hope this makes sense.