Hi,
My uncle has a '77 F150 4wd step-side Custom with the 300. He's had it since 1979 and plans on keeping it for his 6 year old son to drive. The beds floor is shot. He replaced the original wood in the floor in the late 80's. In the mid 90's the floor was getting bad again so he went with the "plywood cover it and forget it". Now the bed is just about falling off. I need to get over to his house to take a look at the bed to see how bad it really is. He wants to fix it or get another bed to replace it. First question: will a short bed fit? Ya try finding a good rust free short bed for cheap, lol. I was thinking about trying to use the floor of a short bed and fix the step side, but like I said I need to see it first hand to see if it's salvageable. If it is what years of short beds can I use the floor from that'll bolt up?

 

I think I understand your question.
A complete short style side bed would fit on a short flair side truck.
To use a style side bed floor would take some fabrication, never seen this done.
LMC has lots of parts for flair side beds, you might take a look at what you would need and the cost.