Thanks, PD. That is not the best news I have had all day - as swapping the intake would have been a simple job while both engines were out of the truck: but at least I can quit looking for the temperature gauge sending unit now, since it does not exist!
Besides lacking the temperature sensor, will I run into any other problems if I leave the '99 intake on the engine in the short term?
That said, I don't want to drive a new motor very far without some indication of temperature - especially a Dodge. The way I see it, there are two possible temporary solutions until I have time to replace the intake (already gave the original back as a core - and have to find a new one and find a free weekend over the holidays!):
1) Install an aftermarket temperature gauge. Problem: Not sure where I would put the sending unit if the '99 intake wont accept it without drilling a hole (which would require pulling the intake in any event).
2) Tap into the existing temperature sending unit - and split off a wire to the gauge. Problem: Not sure if the signal sent from the existing temperature sensor will run the gauge, or if splitting the signal will impact the reading sent to the computer - the truck runs GREAT now, and I don't want to confuse the electronics.