81 dodge project

ive owned a couple dodge pikups in the past but never really did any serious work to them. Now I have an 81 shortbox 2wd /6 auto. guess I would like to know what frames can go to what bodies as I may want to convert to a v8 4x4 and would like to know options. -------short box reg cab to ram charger, shortbox ext cab to long box reg cab, are these options? or should I look for a different truck? ps not afraid of a lot if i can get the right result. All of these are rust free straight options.