There should be a spot on the drivers side of the block towards the front. It's where the oil pressure sender is screwed in. I think its 1/4 inch regular NPT pipe thread. The factory uses and extension in that location ( not sure about earlier cars but 87 - 93 have an extension. A t fitting can be screwed it there for the temp sensor. Steel pipe from the hardware store has been used by some to make an extension. I've personally seen one of those crack on a customers car so I'd never use basic pipe.
Here's a link to the extension. A brass T from Lowes or HD will work.
This 5.0 Resto oil pressure sending unit extension will help you complete your 1979-1989 Mustang engine build!
lmr.com
Depending on how resourceful you are you could drill and tap a factory extension....or have a machine shop or machinist do it for you.
If it were me I'd want oil temperature from the oil pan. That would require a bung welded in.
Are you auto crossing or racing this car ?