Uh, Can't remember. I believe it was 11/32 but I'm not at home right now to double check. If you go the the auto parts store and buy the 1/8" NPT Tap it has the proper drill bit size to use labled on the package. I got mine at O'Reileys Auto Parts but I don't know if ya'll have them in your area. I used a 1/4 socket drive to tap the housing. I found it easier to drive it into the housing. Don't force...No need too. Just start out and finish as straight as possible. once you get a couple of threads cut it should guide you in. Just don't get wobbly.
__________________ Torch Red 07 GT W/Black Racing Stripes, 5 Spd
Performance: C&L Racer CAI, SCT2 Programmer, Bassani Mufflers, Hurst Shifter, CHE K-Member Brace/Torque Limiters, 100% Royal Purple Lubricants
Show: CDC Triple Gauge Pod W/Stewart Warner Gauges, Remote Start Switch, Interior/Exterior HP Badges, Silver Horse Racing Chrome Shifter Bezel, Cup Bezel, and Door Handles. CDC Hood Pins, SS Mustang Door Sills.
Security/Recovery: SLC High Performance GPS Theft Prevention & Recovery System. | 
