wiring

Hi all, Bought a 2020 Promaster EXT a few months back that I'm ever so slowly converting into a campervan. Right now I'm redoing the sound system, and I bought a Dasaita PX6 10.2" touch screen head unit. Where I'm stuck is the wiring. Is there an adapter I can buy that plugs into the OEM harness...

I've got a 2014 Ram Promaster 2500 High Roof I'm converting and I want to cover the whole interior with insulation, wood etc. Then I was working on the rear passenger side cargo area and I found this 12V power socket. I really don't want or have any need to plug into the battery from the rear of...