oil pressure gauge

I own a 88 pickup with a 22r and i would like to install an aftermarket oil pressure gauge, and i wanted to know what size adapter is necessary to install the sending unit into the old location Thanks

1/8 npt female to a 1/8 bpt male.

I have a cheepo Sunpro gauge in mine. Sun actually makes the adapters you need. My gauge was ASE and the block was metric so I bought the kit.