thank you for the info. based on your knowledge of how the heater core is plumbed and operates, what do you think of this setup up below:

put heat exchanger in parallel with heater core
put an inline adjusting valve between the T connector and the HE to control how hot the freshwater gets

should the inline valve be on the input of coolant to the HE or the output of coolant back to the system?

97 Montero SR w/Mitsu Adj Shocks & Rear Diff Lock ARB Front Diff Lock 4.9 Ring/Pinion 3.15 transfer box 43:1 crawl ratio 2" suspen lift 2" body lift 2" Gas Tank Lift 35x12.5 MTRs 15x10 Wheels Rock Sliderz ARB front bumper w/12k winch Custom rear bumper