I just wired in a 24 to 12 volt converter to my Deuce.
Already had main battery/power cutoff switch in battery box, so wired from it to converter then out to separate 6 circuit fuse block for 12 v. only stuff.
Also wired a separate 24v. fuse block for heater , lights, etc.
Both systems share chassis ground on truck frame.
Mounted fuse blocks on inside back wall of glove box and made plastic divider wall in front of it to keep things away from them.
Wanted to keep all add on items off the original truck wiring system as it has no fuses, just a circuit breaker for whole truck.
Working great so far.