On a 394, assuming I leave the original light hooked up, where's a good secondary spot to tap in for an oil pressure gauge?
I got an electric gauge so the sender is fairly good size.

 

The same place the current sending unit is connected. Put a Tee there and hook both up at the same location is what I would do.

 

The sender screws into the top of the oil filter adapter. To get good access, you may need to remove it. It has 4 bolts in it.

 

Pressure senders don't care how far away from the engine they are. You can use brass pipe fittings and nipples to tee into the stock sender location and split off a port for the aftermarket sender. Put it wherever it needs to be.

 

Thanks all. I'll take a look this weekend and T it in.

 

A tight fit but doable.