The Autolite inline 4 barrel carbs were developed as a way of dealing with the single 4 barrel rule imposed by the SCCA in Trans Am racing. The thought was since any 4 barrel carb was allowed, why not make a unit with the barrels all in a single row for better distribution?
Inline carbs came in 2 versions. Part number DOZX 9510-A, aimed at Trans Am and NASCAR racing, used 1 11/16" throttle bores and was rated at 850 CFM. Part number DOZX 9510-B, aimed at drag and unlimited class racing, used 2 1/4" throttle bores and was rated at 1400 CFM.
Ford made just 1,000 Autolite In-Lines and 100 Cross Boss manifolds before production ended.
Of course, why they've faded from memory is the usual reason, more conventional Holley carbs worked better on the street and were easy to service. The Autolite inline 4 was much better over 5k rpm for racing.
"Cross Boss" is actually the name applied not to the carburetor, but the intake manifold it was designed with. This was a two-piece design with Ford part numbers D0ZX-9425-A and D0ZX-9C483-A.
when it gets to talking about rare musclecar carbs, this one is always forgotten