Last night I finished up the water pump job on the '71 Swinger. Since that it was the first time I've ever replaced anything on an engine besides spark plugs I am pretty stoked. Thanks to all who gave me advice before I tackled it. The pump I ended up buying was from NAPA, and was made by GMB in Japan.
I can no longer hear the noise that the old pump was making -the new one is quiet. Other impressions - it was slightly difficult getting the new pump behind that plate that the A/C unit is mounted to (just like SlantSixDan said) and I was really worried that I would screw up the gasket and the seal since I couldn't really see what I was doing. Every single thing I had to do to do this job was a new experience for me, I'd never even taken off a belt before. Now all the belts and hoses are new.
I bought the '71 Dodge Service Manual and was referencing it, but it is assuming a lot of previous know-how (like it says "drain system, remove belts, remove hoses, remove and replace water pump" - easy!)
Anyway the Dart seems to be running fine (at least as well as before) after taking it around 5 miles of Brooklyn last night. No leaks! I guess the true test of how well I did will come months down the road, if it's still not leaking or throwing belts.
And now.... I have more questions for you fine folks.
1. I wonder if the car is running hot. The radiator is non-original and I don't know how it stacks up to the stock rad. During my short cruise last night the temp gauge needle was getting close to 90 percent across the presumably "acceptable" range and would get down to about 70 percent when the car was moving. It was at 1 am, but New York was still 90+ degrees. I stupidly did not replace the thermostat when I did this job, I know it's cheap but I just didn't think to do so. I don't know how hot the car ran when I first bought it because neither gas nor temp gauge was working. Mysteriously both started working after I changed the turn signal bulbs.
Should I just drain it and replace that thermostat before I ask any more questions? 
Should my gauge be reading around the middle most the time? 2. How can I determine if this radiator is appropriate for the Dart? (Besides the fact that the drain at the bottom shoots the fluid during draining into the frame and therefore everywhere?) Believe me, I'm not in a hurry to buy an expensive radiator but also want to make the car run right, first and foremost.
3. How should I approach fixing the heater and the A/C? Right now the heater buttons and controls make nothing happen. My friend who was riding along last night starting fiddling with the heater controls after I was mentioning that the temp needle was rising higher than I was expecting. He was ready to start blasting the hot air out but we discovered that we couldn't do that even if we wanted to. I have no clue how to approach troubleshooting a heating system. The only button that made something happen was the A/C button. It sounded like it activated the unit under the hood (sounded kind of loud and unhappy) and put an obvious load on the engine, but there was no air coming out the vents. To be honest we didn't expect that to happen and quickly shut it off. Where to start? (Sorry if this is off-topic for the engine section)
4. Since my car was a factory A/C car would it have come with a fan shroud? It's not there now if it did. Would that help the car keep cool in stop-and-go? If it's significant, where should I get one?
5. Is that enough for now??!!!
There is a lot more general mechanical and Dart-specific ignorance where that came from, trust me! I'll be damned if I won't overthink everything, too. Thanks again.
DB
