One thing that may not be obvious - did you also change to the serp belt water pump?Further downstream...if it isn't the t-stat, then I think 'water pump' - it now has a fancy 8-rim serpentine pulley, which has a nearly identical diameter to the OE v-rib pulley it replaced, and the crank pulley is also nearly identical in diameter to the OE unit, so the water pump speed should be pretty good.
I'm thinking about getting a Wizard radiator for my 2000 Durango 408. Are you happy with one you recently bought? Also, are you using it with the factory fan setup, which I assume would be a large clutch fan plus an auxiliary electric fan that come on with the a/c and at around 200* or so without the a/c)? Or with an aftermarket electric fan?yup agreed. I spoke with Scott and Sean at Wizard, and...well first they have a number with actual humans at the other end that actually answer the phone . They have 4 versions of the Dakota radiator - two core thicknesses (2" and ~2.75"), each with or w/out the heat exchanger, which can be had with or without the fan and shroud assembly. They had slightly blemished version of the big phat one with the exchanger in stock, which they offered me at a discount, and I ordered it without the fan/shroud (but it is nice to know it's available). I can't think of a much better solution, and even if the radiator isn't the cooling problem it for sure won't be the problem down the road, especially when I start driving it hard and hooking up a camper trailer - I'll take the maximum cooling capacity possible all day long.
I spoke with Sean at Wizard Cooling and told him you said 'hi'. He remembers you and told me that he still has the radiator you returned to them, the one with the 1" tubes instead of 1.25" tubes. He said he would give me a little break on the radiator you returned for the thicker one, but he mentioned that it's not cosmetically perfect. Were you aware of anything wrong with that radiator at the time you sent it back to them? ThanksLove the Wizard rad I got - it is the big extra-thick one with the internal heat exchanger. But my fan setup is very definitely 'not' factory - I have a 440 with a mechanical clutch fan and a very custom shroud, so I can't speak to how well the OE tupperware bolts up, but it is supposed to bolt up all per factory. I think you'll be very pleased with one . When you talk with them (Sean or Scott) tell them Sam with the big block Dakota says 'hi'.