the head is 1/8" NPT, I know when I had oil pressure/temp gauges on my 5sfe I needed an adapter to 1/8" BSPT... here is directly what zoni sent me when i installed them:
"Yes for the pressure you put it where the stock oil pressure switch is. If you arent going turbo, you dont T it.. just replace the stock one with the gauge one. BUT... you need a converter from 1/8" BSPT (british standard pipe thread) to 1/8" NPT which is the standard we use here in north america. It is different because the thread pitch is different. 1/8 BSPT i believe is 32 threads per inch or something, and 1/8 NPT is 27.
The part you need for this conversion is Autometer part # ATM-2269. you can get it from summitracing.com for less than 15 bucks. Also, other dealers carry similar products to this that arent sold by autometer. those are fine too."
Image of what it would look like with a t:
hope that helps man!
Damon