Have a 92 4x4 long bed and I want to shorten for a short bed... can I trim 6" out of existing frame or do I have to swap out rear of frame? If I have to change the rear frame out what models would be compatible?

 

That's a rare model

Yes, you could cut 6" out of front section of rear frame and also 6" off rear section, so might be better, easier to just grind off the rivets and swap rear frames
And you may be able to SELL an intact Long bed frame to get back some costs, these long bed frames rust out like any frame, lol and are much harder to find
People also like to make Extended Cab Long beds, which was not a factory option, so are looking for Long Bed frames AND Beds

There were only 2 sizes of rear frames, short bed(6ft bed) and Long bed(7ft bed)
Regular cabs could have either
Extended cabs could only have 6ft

Front frames had 4 models
2WD Regular cab
2WD Extended cab
4WD regular cab
4WD extended cab

4WD had boxed frames in the front for axle mounting and less flexing

 

Does the 92 have the 2 piece frame that is riveted? I was under the impression I would need to z cut and weld...
and for a rear frame for example could i use the frame say from a 97 2wd extended cab w 6' bed on my 92 4wd long bed to shorten for a short bed?

 

It may just be 1998 and up that used the rivets, earlier are welded, but all were two piece frames, because of short bed/long bed and in 1986 regular cab or extended cab

 

I will look at mine to try to see what's there thanks