Assuming you are just going 30 amp service consider a new PD distribution box with built in 12v supply and both 120v breakers and 12v fuses all together.
http://www.bestconverter.com/PD4045-45-Amp-Inteli-Power-Mighty-Mini-Power-CenterIncoming wire from the 30 amp cord should be #10 and branch circuits with 20a breaker need to be #12 and any 15 amp breakers should feed #14 wire. Standard romex style wire is fine for 120 vac. You will have a 30 amp main breaker in the panel to attach the incoming wire from the 30 amp cord.
12v side... insert fuses to match the wire size. I would use stranded marine tinned wire for 12v connections.
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