Well, the NOS air cleaner box came with only one bolt of the four that are needed to attach it to the carbs. That bolt is a 5/16-18 x 2 1/8" which is I believe, a UNC thread. I managed to find two more identical but aged bolts in my miscellany box (every garage should have one) which probably came from my first Vitesse back in the 1970s. In need of another bolt, I thought I would check my workshop manual (page 0.111) to see what the spec is and was surprised to find that the book lists that bolt as a UNF.
Here's the but... 5/16 UNF are 24 TPI while my bolts are 18 TPI which makes them UNC. Is the book wrong?