It is a Toyota starting battery. Does your 80W panel supply enough power to handle the fridge(assume ARB 63) without having to startup the truck?
Assuming that you only have 30% battery capacity on your starting battery to safely use, the 80w will still require starting the truck and using the alternator, my "best guess" is the 120w will be your best bet for using this current setup.
Some of the other factors that come into play are, how often are you accessing the fridge, beers and buddies will warm a fridge quickly requiring more juice. How much sun are you getting thru out the day, what are the ambient air temps day and night, etc?
Personally, with my electrical demands, which are greater though I have a dual battery setup, I prefer the 80w panel: inverter, fridge, stereo, phone charging.
I have no personal experience with the 120w only the 40 and 80w.
Give me a call and we can chat over the pros and cons. 646.ExpedOp
Thanks,
Jeremy