Hi Matt.
It as a wilwood after market MC. 5/8ths bore. (or 11/16ths can't remember)
I made the adaptor plate from some ally.
Just grab some plate thats quite thick - remembering it will take the force of the pedal.
Drill holes to match the bolts on the fire wall then counter sink two bolts from behind (tightly so they don't spin)
to match new MC and then bolt it up.
You'll also have to fab a link from MC to pedal. I have that yet to do.
If you search the site i asked a here and there about it so the info is around.
Good luck, happy to help with more Q's if u need but bear in mind i have not operated this yet.
More pics to come - just finishing off the rear disk conversion and 4 pot wilwoods on the front.