3/8"unc 1.6250" long stud for engine block to accept the TAM2097 screw on filter head and for HS2 carbs, alternative to this is CHS2614 @ 1.75" long (just over one thread longer). LYG10008
bolt was later alternative for the filter head.
UNC course thread for manifold or block and UNF for the nuts. See also 22A152 longer stud for some HIF carbs.