a blurb on trans coolers
http://transmissionrepairguy.com/transmission-cooler/
blurb on mounting ideas and air flow etc
http://gojeep.willyshotrod.com/HowtoAutoCooler.htm
some ideas on how a remote frame mounted cooler and fan would look
https://www.amazon.com/Aluminum-exte.../dp/B00WRIA1Q6
another blurb on cooler types and how they work
https://www.transmissionrepaircostgu...ission-cooler/
when I used to build rail buggies I would always install a large light on the dash that was connected to a low oil pressure switch. you could do the same only use a temp switch instead. wire it temporarily until you get a baseline established for driving style, hot days, heavy loads etc. then remove it or install a more discreet warning system once you get the system dialed in.
remember that if you use an electric fan to cool the engine you may need to also wire the fan to run when the a/c is on. a 2 fan system may be beneficial in that case. a/c is going to drop some more heat into the rad area and a trans cooler will also add heat. that is why I mentioned the frame mounted trans cooler.