[Roadsters] oil pressure guage

[steven boortz]

hi everyone
i'm trying to fix some things on my roadster before heading to the track again.  to that end, i'm thinking of replacing my stock oil pressure guage.  i had some funny readings the last time on track and wish to see what the real deal is.  i've heard mechanical guages are better for track use.  does anyone know what size is the hole in the block into which the sending unit is threaded?
thank you in advance
steve 675MIZU