Hi,
I'm note sure the original switch on your engine is a fan switch. I think it is a water temperature sender. On the Pinto, IIRC, originally, the fan is mechanically driven, so there no reason there would be a fan switch.
So in my opinion, you have a temp sender, and you'll need to add a fan switch on your cooling circuit.
For the oil pressure sender, yes, you can use the place (tapered hole in the block) where the original oil pressure sender is, but you will need to use the sender that comes with the gauge. The original oil pressure sender will not work with an after-market oil pressure gauge. And make sure to know the thread of the original sender to use the right adapter.
Hope that will help