D rings mounted to seat bolts and straps along with separate power point
Hi Matt,
While waiting for Ram owners to reply, hope this might help.
I don't have a Ram, but I did mount a fridge behind the front seats of my Jeep, so maybe these pictures and description will be helpful.
This fridge is the Dometic 65qt dual zone.
I used cables and turn buckles to the seat mounting bolts to secure it, and makes removal quick and easy.
Used aluminum plates to replace the handles, but if you use straps this wouldn't be necessary. You could just use D-rings attached to the seat mounting bolts. With the straps and fridge removed you'd only have the D-rings in place.
It doesn't take much tension on the cables to hold it very securely for even extreme wheeling.
On the electrical side, the fridge has a built in power cut off. Depending on model it may have up to 3 settings. For a single stock battery, the middle setting works well.
I would recommend running a power port directly from the battery into the truck, rather than use the truck power ports. Using a stock power port really pushes the limits for a larger fridge, and you'll get voltage drop which will cut the fridge out sooner than necessary.
I purchased a 12' power extension cord from Amazon, cut the male end off at the correct length, added an inline 15A fuse and eyelets right to the accessory lug on the battery terminals. 0.0V drop this way.
Here is what I purchased. It's made in China

() but it is good quality.
https://smile.amazon.com/gp/product/B00P68L9RO/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
Any way, I hope this proves helpful. If you run with a passenger, I'd suggest putting it behind the driver's seat. This way the passenger has quick access to food and drink while on the road/trail. If you run solo a lot, it's very handy to have it behind the passenger seat.
Second picture is one of those "jump packs". For a single battery setup this pack works amazingly well. I still carry cables, but doubt I'll need them.