Wiring looks fairly easy to follow. Just have to get another 3 way switch and figure out where to put it as the body looks like it has only been routed for 2?

Another 'heads up' would be to grab 250k pots for the single coil J Bass PUP's and maybe a 0.022mf Orange Drop Cap and use the 500k pots for humbuckers together with 0.047mf Orange Drop Cap. If you have never done a treble bleed mod, highly recommend it and they are only $2.95 each.