Redrilling drums

FWIW, if the drums still register on the center hub of your new axles the drilling for the 4.5" bolt pattern does not have to be super accurate. If you look at most drums there is quite a bit of clearance between the hole in the drum and the stud. You could pick up a wheel spacer at the local wheel store and use it as a drill jig.

If the center hub does not accurate register the drum then you will need to have some on that can accurately position the holes so the drum will register off the studs.