[6BT 56]

Glad I could help with the wheels . I saw your post when I was catching up and saw the comment abt the wheels and thot I needed to chime in to prevent you from having the trouble and expense I did. I just put similar vintage caps on my 56 . They look period correct for a lot of old trucks Maby look into some steel wheels for a 2002 and newer truck . They must fit over the callipers and maby ??? Can fit a hub cap???

With your wiring issue dosent the eng have multiple relays for ecm crank fuel pump and so on ? Isn't the key switch just triggering the relays with no direct path to the ecm? If that's the case not to likely to Make the ecm take a dump. Just my thoughts , come on in of the ledge pls . Lol