66 Dart GT HT Whatsitgonnabe?

Don,

Ulf actually already promised to send me a pulley so that problem should be out of the way! He'll be sending me some bolts, too.

The water pump lines up nicely with the alternator but the alternator is new so that could of course be an issue. How do I identify the water pump?

Ulf knows his stuff; if he sends a 69-earlier crank pulley I bet that will fix your misalignment issue. You might have to elongate one of the crank pulley bolts so it will bolt to the 360 balancer. If the current water pump pulley lines up with the alternator pulley, I'd say you should be OK there and everything should line up when using the 69-earlier crank pulley. I've found that matched sets work the best.

I'm planning on using the original instrument cluster with an additional set of gauges. I don't know if there is another hole in the block where I can put the idiot light oil pressure sender.

Then to make the oil light on the instrument cluster function, you need the correct sender for it. The one on the motor is for a factory gauge and won't work. If the additional gauges are electrical, then the sending unit must be compatible with the oil gauge and usually comes with the gauge set. There is no other hole in the block so to make both work, you'll need to use a Tee. On my wagon I have the digital oil pressure gauge and an idiot light and will use a Tee that both sending units fit.

I guess the neutral switch is from the 904 transmission I no longer have. Or there would be a pretty big hole somewhere, no?

Those neutral safety switches work on either a 904 or 727. Yes you'd have a pretty big hole in the transmission and fluid would definitely run out :D

There's a PB outlet on my carburetor. Am I better off using the one on the intake?

Are you sure the one on the carb is not for the PCV; they are about the same size. I'd use the one on the manifold!