Stepside --->> Fleetside

I'm thinking about buying an '86 stepside but I would want to change it to a shortbox fleetside. The stepside is rusted out anyway, but would the fleetside flop right on the frame or would I have to change something??? Thanks

Should bolt up just fine. Should use the same frame holes. I took a utility tool box bed off of my '85 C20 and bolted a fleetside long bed on. Frame holes were all there.
Clark