N3310L, N91S, N92S, and N94S were all operated by Southern Airways in the early stages of their lives :
N3310L from 8/73 to 7/79
N91S from 5/67 to 7/79 (was leased outside for one year during that time)
N92S from 6/67 to 7/79
N94S from 2/68 to 7/79
As we all know, Southern Airways operated very short flights with quick turnarounds in the southeast US before they merged with North Central in 1979 to form Republic, which later was merged into Northwest: so the lineage was definitely there.
Tom in NO (at MSY)
PS: I've got a picture of N3310L I took at ORD in '79 (Southern colors) on my office wall, I'd be interested to know how many hours and cycles it ended up with before it was retired.
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina