Water pump pulley ratio high RPM offroad

If space is cramped, and it sounds like it is.
Then the more efficient the radiator is the better off you will be.
Do some research of radiator construction and it cooling capability, then pick a efficient radiator, that fit your space.

You say other like yours don't have a heating problem, HP= Heat! Turbos are creating heat from power as well as under hood heat.
I see you have a nice open hole in the hood. that's a plus.
Is your air filter getting cool air or is it inhaling hot air from under the hood.

Ign timing could also be a factor.
Remember, cruising down the highway, your not using up all you HP.
Sand suck HP out of your motor all day long. takes HP to have fun in it. Radiator has to match.