Best bang for buck 6.5 cooling upgrades

[Husker6.5]

It sounds like original poster was trying for lowest cost for biggest result. Of course, if he put on the 97-99 HO water pump, with the necessary switch over from "V" to serpentine belt drive, he's getting higher flow than the 93 style pump but the right head is still getting the lesser flow of the two heads. The upgrade to the 2000+ pump is fairly cheap (if doing the labor himself) upgrade to cooling ability and ensures both maximum flow and balanced delivery to the heads. Add in the 15°F lower (180°) kick in of the Kennedy fan clutch and more air moved by the D-Max fan and that should cover temperature issues in at least 95% of driving/towing situations, unless you're a towing demon that puts way too much stress on the 6.5 and then engineers his way out of killing motors like @WarWagon has/does.

 

[emmott]

Here's what I went with on my 97+ C/K trucks

GM 15029405 Radiator Fan Clutch (spin on type clutch)
ACDelco 251603 Water Pump (spin on type clutch) (latest OEM revision)
ACDelco 1580690 LB7 Radiator Fan (radius ≥½" above OEM, may need new motor mounts or shave inner lip of fan shroud to fit)
GM 89018624 Radiator

96 C/K Thermostats & Housing
GM 12559338 190°F Thermostat (use ACDelco brand, others have poor reputation)
GM 12551519 Thermostat Housing
GM 12554528 Water Outlet

97+ C/K Thermostats & Housing
Leroy's Restricted Bypass Fitting (Supersedes GM 12486391) (others on a shady budget have slid the largest socket that fits inside OEM fitting to restrict flow)
GM 19137270 195°F Thermostat (use ACDelco brand, others have poor reputation) (need two)
GM 12553407 Thermostat Housing
GM 12564276 Water Outlet

 

[MrMarty51]

I am thinking of going with twin 185 T-Stats.
I have a new coated radiator from Twisted Steel, the super flow pump from Leroy and need to install those two items. Already have the Kennedy Diesel fan clutch and the restricted fitting from Leroy Diesel. While the coolant is drained going to install a temp probe into the right rear head and monitor the temps back there.