Thermal clutch fan or non thermal clutch fan

[NC72crew]

So im finally getting some progress on my crew cab. I bought the vintage air system for it and i want to install a clutch fan instead of using the fixed fan. Do i need a thermal or non thermal cluch fan. I will be driving in the mountains some or pulling a camper with it so i may be going slow up hills in a lower gear causing the engine to be revving higher at slow speeds. also what size fan blade should i buy for it to fit the fan shroud i havent bought yet?