Late '70s- early '80s Granadas, Fairmonts, Fairlanes, the usual mid sized grocery getters that tended to rot out, get scrapped and are getting hard to find Flatman
just what kind of 6 cyl are you looking for? the little Falcon based 170/200/250, or the big car/truck 240/300? they are quite different engines, with a different bellhousing bolt pattern.
the smaller engines were used in Falcons, Mustangs, Mavericks, Granadas, Fairmonts, and the Merc versions of these. 1984 seems to be about the last year they were used.
The 240 and 300 have the same bellhousing pattern as the SBF, so any C4 that bolts to the 289/302 will bolt to a 240/300. Just need to match the flexplate (157 or 164 tooth) and the block plate to the bellhousing. The little 200 sixes came with C4's from the mid sixties thru the late 70's. About 1980 they started to be equipped with the light duty C3 and the lockup torque converter C5. They look similar to the C4, so check the pan pattern to be sure. The little six C4 can be used behind a big six by changing the bellhousing and the torque converter. Rumor has it that the A4LD can be adapted to the little six by using the C3 bellhousing.
Wow... exactly what I'm getting ready to slide into the '60 Falcy. Early Mustangs had 200ci inlines and C4's... almost a direct bolt-in (for a Falcon anyway), then find a Maverick 8" rearend, and you are almost on the road!
Oh... and almost everyone who gets a stock Mustang immediately throws the 200 behind the garage and stuffs a V8 into them... they are everywhere man.