Question: For what years are the beds interchangeable, or at least dimensionally very similar for shortbed trucks?

I'm fixing the bed of my '73 F100 shortbed. The front of the bedfloor has some large rust spots against the front of the box and the sides. Also, two of the cros-smembers are spongy in places. After talking to a guy at a car show, I think the easiest repair will be to find a donor bed at a junkyard and cut out the floor and weld in the donor bed (or at least a big chunk of it). I've heard that 1993 and older beds are basically the same size, but I'm pretty sure the bolt pattern changed (8 to 6 bolts?). While drilling a hole in the bed is not hard, the beds have the recessed areas around the bolt holes and I don't want to have my repair look like crap. Obviously finding a good condition 73-79 shortbed is the goal but likely impossible, so if I newer Ranger bed will fit, that makes my life easier.

 

Sounds to me like you may have answered your own question. Rather than replacing the entire floor, you would be better off just cutting out pieces and welding them in place. If the later model trucks have a similar profile, that should take care of the problem. If the front "rail" of the bed floor is completely gone, start with a pice of angle or have a peice of flat stock bent at a 90 that runs the full length of the bed.

You can also buy patch panels from LMC that are pretty reasonable and they match up with the original metal. A trick that I used was I bought an entire bed floor for a step side and dropped it into my styleside.

 

I would say your best bet would be to find a buddy's truck or a junkyard and start measuring.

 

I let this lay dormant for too long, time to post my work. I found 73-95 F series beds all have the same dimensions. But the bolt pattern is different. So I cut a patch out of a donor at a LKQ in Raleigh and cut out my rusty section. I cut out the spot welds and removed the second cross brace from both pieces. Then I (meaning my friend) welded the old brace to the new patch. Now 6/8 holes can be used.

In my case, the middle of my old front cross beam was spongy, but the ends were fine. So I cut out the middle, left the ends, and cut the ends off the donor. I had planned to mostly spot weld the new parts in place, and this strategy minimized the amount of wire welding. If course the HF spot welder died mid way through and we mig welded it up anyway. Also, beware, cutting out such a large section allows the bed to flex and distort. I used straps to hold it together, but any larger cuts and you should welds braces in place.

Final note- newer beds have less sharp currogations of the sheet metal. It can make lining up the back seam difficult. This is not perfect, but a little bondo and bedliner and it would barely be noticeable.

 

For what it's worth a 2015 Super Duty floor has the same floor bolt pattern as the wide frame dents. The floor pattern is different the 2015 has an area where a fifth wheel would go stamped in the floor. Does not come with the front or rear crossmembers the front is the same but the rear is different. The price for a 6.5' box which I didn't think was to bad was 500.00 Can.