You'd still have to deal with the SKIM (security module). Once a SKIM and PCM communicate through the bus, they are initialized to each other. You cannot run another PCM with the same SKIM nor put a used SKIM with any other PCM. In order to get around this problem you'd need PCM's that were never initialized to a SKIM (so reflashed ones that were never installed in a truck with SKIM) and to remove the SKIM from vehicle, or get a new SKIM and have separate ones for each time you swap the PCM (which would also require separate chipped keys to operate). Your best bet here is to remove your stock PCM, get it reflashed (I believe there are aftermarket companies that can hook you up with this) with the engine program minus any security, then remove the SKIM (the module itself) from the truck. All things being equal this should allow you to swap PCM's around as you like without worrying about locking them (yeah, if you keep doing that where you start it and then it shuts off too many times it'll lock the PCM and it won't start at all). I cannot guarantee this will work as there are too many other communications going on within a CAN bus system; only way to find out is to try it.
