Thread pitch on Clifford 6=8?

[huntnfish08]

I've got a Clifford intake and would like to put in a vacuum barb. There is a hole centered below the carb mount that a 3/8-16 bolt will thread into but they don't seem to offer that thread to barb adapter.
Any help on this thread pitch?

 

[bubba22349]

Should be iron pipe threads, Try a 1/4 inch NPT. Good luck