I don't know how much this is going to help you, but here goes. Recently I've been going through parts in my basement to sell, some of which I haven't seen since the 70's. Anyway I think (someone correct me if I'm wrong) except for the chrome lid the L48 and the L30 air cleaners are the same. I found two L30 air cleaners a '67 I believe and a '68 both for a manual transmission. The '67 base measures 16 5/8 in. outside and 16 1/8 in. inside diameter. The '68 base measures 15 1/4 in. outside and 14 3/4 inside diameter. Hope this helps, RonM.