Got a broken black/red wire coming from driver's door front into area leading to behind the instrument panel. Looks like a previous owner tried to splice it there and failed. Gonna trace it from end to end and replace it with tubing around it. What gauge wire is recommended for replacement? I'm thinking 16, but want to verify before I order a 50' spool, which I'm sure I'll need in the coming months of restoration. I'm planning to pull the door panel, and hopefully this wire is coming from one of the fuel tanks and why the gas gauge isn't working. If not, something is gonna get repaired anyway. Thanks.

 

16 guage will work but you may consider getting 14 just in case you run across something that needs to carry more amps during your restoration.

 

A quick look at diagrams, found black / red being fed from the fuse box (Fuse #2 14 amp) to the backup light switch then to the backup lights themselves.

 

I have generally erred in favour of taking a wire size larger when replacing wiring, as a vehicle ages so does corrosion at links/connections and especially newer vehicles that have very marginal wire sizing in order to keep costs low.
A prime example is the battery cable sizing now compared to the past, especially as, a say starter motor, ages, it will often draw more current than new, especially with an older battery no longer meeting full voltage spec, the current rises and load on wiring increases leading to burning of starter windings.
Battery wires are something I always upgrade or replace when restoring or servicing older vehicles.
Same for long runs of wire that appear to be deteriorating.

jus sayin' Ross.