A simple low buck fix. Fab a spray bar for front top of the radiator core, simple pipe w/ small holes. Attach to a gallon or 2 water supply & divert your windshield washer pump or any 12v switch controlled pump. The gauge will drop in minutes.
Not at all familiar w/ your ECU set up. However some get whacky from radio interference. Easy enough to disconnect the hot to the radio or any com device in the truck.
I ran duals for a year on the K20. Black valley flashing screwed to the wheel well lip looked better than the numerous busted fiberglass fenders seen around here. I abandoned the duals after one winter of following the crown to the barrow ditches.
Ive done trailers, 55 chevies & K20 with build it yourself components from Superbrights. Devastatingly bright & very inexpensive.
https://www.superbrightleds.com/vehicle-lights
Welcome, Payson used to be my escape from the valley in summer. Hell’s Gate was my fav get away.
Likewise couldn't find cab mounts. Ended up using hockey pucks