Hi mate, the ones I swapped out of my J Bass had red & blue wires and one of the PUP's was shorter than the other as follows:

Blue Wire: 91mm wide

Red Wire: 94mm wide

This tends to suggest the narrower one is for the neck position and wider goes at the bridge. A multimeter can also help as the lower rating usually goes in neck position. Sometimes a longer wire than the other PUP gives a hint as to which goes where too.

Not sure what you mean about the pickguard and probably need photos to figure that out.

Cheers, Waz