...woot! - it fits!
The 46RH bolted up to the same crossmember bracket the 46RE used, which 'located' the driveline same-same as the 360/46RE was. Bolted up the 440, and test-fitted the core support leaving all of the Dakota OEM radiator Tupperware in place - it didn't fit nearly at all - was about two inches shy of bolting in place and clearing the fan. I unbolted all of the Tupperware, then unbolted the aux electric radiator cooling fan (which I don't see any need for in the first place with a mechanical fan and fan clutch), put the core support back on, and the 440 fits just like it was supposed to be there, including a nice 1.5" of clearance between the fan clutch and radiator. Plus, with the 3" body lift the radiator moved up which perfectly centered the radiator with the 440's fan - bonus. I'll fab up a fan shroud, coolant and washer fluid reservoirs, and that's that. I'll set the cab back on the frame and confirm everything for good, then with the cab, core support and fenders all bolted up I'll confirm the front axle placement, and once that's done I can finally confirm what kind of oil pan I can use. Once that's done the rest is just connecting the dots.