1967 M-715 Rewiring Advice needed

[44willysmb]

I am looking for advice here for rewiring. I have read various threads here and other places and have gained pros and cons. I have a 1967 M-715 that is in great shape but the wiring is suspect. I acquired an old fire department brush truck that was well cared for (mostly). I am leery of the spider web of spliced wires hear and there. They converted it to 12 volt when they blew the original engine and installed a 283 SBC. I am happy with it and will keep it. The question boils down to which way to go on rewiring: a Painless wiring rewire or modify an M series loom (m35A2 or M151)?

I wish to use the 3 way switch again with the functionality of the blackout lights. There is a keyed ignition that I will also keep. Nice that it makes it more difficult for it to be stolen. Apparently the M151 wiring may be more appropriate since the alternator wiring is on the correct (driver’s) side. But actually having fused circuits with the painless would be a peace of mind too. Thanks for your thoughtful comments.