i just got one from orielly. I can get the part number if you want. it looked a little smaller than the orig one. I haven't installed it yet.

A part number would help when going down there. thanks. My '51 had a gauge screwed into the elbow at the block....a little tough to read. The '51 I parted had a SW mechanical gauge which I may reuse....someday. Terry

There are many versions that will work fine. A style that is common is the NAPA ECH OP 6613 which is a 1/8 NPT (1/8-27) mount and has a threaded stud for wire attachment. If you desire some other terminal tell the parts guy and he should be able to find an equal. It's a 2-6 psi switch, which is low for my tastes but, if you really want to know what the pressure is, you'll need to install a real gauge, as you well know. An idiot light is still a good idea, though.
Be sure it's an 1/8 NPT (1/8-27), not 1/8 BSP (1/8-28).
Frank

I had one on my shelf that was for my Mom's '93 Ford Escort, it was a perfect fit except I had to change out the electrical connector!

Walt here; ask for a stewart Warner part #32 at any auto store and they can change it to the number they sell.