the 67 326 with A.I>R is correct but with your 68 there are three different listings in this catalog. Just a 350/2bb/ then a 350/2bbl with 3 hoses and then a 350/2bbl with 5 hoses
FWIW I have recently found that a different catalog from this one (67-74???) has different GM numbers in it. I would suggest looking into getting one or both of these catalogs and searching the parts numbers that way.
Hopefully someone else will chime in an tell us which of these catalogs is gtg or if one is Canadian or some [censored] thing?
