Bolt Size- 56 Tbird

[paul2748]

My Tbird was always an autmatic. I've been doing some work on lt and decided to put a bolt in the holes in the frame that holds the bracket for the clutch pivot (Z bar). I know they are not 5/16, more like 3/8. Does anyone know if fine or coarse thread? Tried both and nothing wants to easily screw in. Probably a lot of crap in the holes, so I want to run a tap in them

 

[dmsfrr]

These are 3/8 inch, coarse thread. (manual trans '57 Bird)

(edit)
I just tried a 3/8 coarse thread bolt in the same two holes of a '55 w/ auto and they fit fine.
.

 

[paul2748]

Thanks