Alright I've been working on turning my 79 4x4 f150 reg cab long bed into a short bed flare side. I have everything disconnected on the frame where I need to cut the 16" out the question I have is right where I need to cut is where the frame widens up at( behind cab between first and second bed bolt holes) When the 16" are cut out of the frame the rear sections is going to be about 2" wider then the front section. How to you get them the line up again? Make a relief cut and beat the frame in then weld it back up? I don't trust myself with the welding so I'm taking it to a guy that's a welding guru but Id just like to have some helpful info to pass along to him.

 

Before cutting, weld cross bars to keep the frame aligned and vertical legs for support and to keep everything level.

The frame needs to have a Z-cut like pictured below (it's a C10 but you get the idea). The cut on F-series is made immediately behind the cab where the straight frame section is located. Then a fish plate is welded over each Z-cut. Inside or outside, your call.

There is no beating allowed to make it line up... you are only asking for trouble by persuading it into position. It needs to be a natural alignment.

 

What frame is that in the picture? My frame starts to widen right after the cab. I almost wonder if a few inches where cut out that the rear section could slide over the outside of the front frame and overlap each other.

 

whoops I seen what kind of frame you said now.