After rereading that thread I have decided what I would like to do with my 87 Syncro Tintop Custom interior camper.

1 - Add a 2cd house battery under drivers seat.
2 - Make it a isolated house battery (if need to jump primary batt Ill use jumper cables to it).3 - Isolated means I can charge it off ALT directly but need a separator ?,  6 gage wire OK ?
3 - My load would be 12 v fridge (Dometic sit on floor fridge, radio, charge station for phones/laptop etc)4 - Upgrade some of my wiring while I am at it. I have a 2000 2.5L Subaru Impreza engine conversion.
5 - I might install the SA Grill and headlight upgrades in the near future.

So it looks like recommendations are:1 - Separator:    Victron or BlueSea 76012 - Battery:        Odysses PC1750 or Lifeline ?? (sealed AGM is preferred)
3 - ALT to Starter wire upgrade = 6 or 4 gauge (I might already have this from the Subaru harness, will check)
4 - new wire from ALT to new battery/isolator ? or this is spliced in from the main batt ALT wire to isolator ?
4 - upgrade any old Vanagon battery wire I might need to while at it ?
5 - add solar charging to it later. Sounds like it would just need a direct connection and a regulator ?

As well I would like to install a relay to provide the starter more juice. I did this on a 81 Westy I used to own with the help of my local mechanic. But have since misplaced my wiring notes on it from years ago.

Seeking expert advice out there for these connections, recommendations...
TIA Sean G