Well insulated & Electric Heater = Trouble IMHO
Go over to The Samba/Vanagons search for Propex, tons of info
also look at Carls stuff, great guy, tons of info
will give you the 411 on propex and truckfridge
6v batteries? run together to get 12 v?
how many amp hours?
how you gonna charge them?
My Two Satang:
1) get 200 amp hours worth of battery storage
2) get a HD alternator and a Sure Power or Blue Sea Isolator
3) Consider a solar panel
4) if using the honda to charge the batteries, make sure you have the correct charger
5) with enough amp hours, correct engin chargin system, dont know why you need the generator