Found this on the net Chris...
Autolite Inline 4 Barrels
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 developed a companion 2 piece Cross Boss intake for use with inline
carbs on Boss 302 engines and, with spacer plates, on 351C's. The basic
Cross Boss arrangement consisted of a lower plenum, part number DOZX 9425-A,
with a bolt-on top cover, part number DOZX 9C483-A. The removable top made
porting easier. In classes that were not limited to a single four barrel,
an 8V cover was available that, in Ford's words, "provides one barrel per
bore, located directly above the intake passages". It is unclear from the
photos I've seen if this arrangement used independent runners or a plenum.
In any event, inline fours could be adapted to Weber or fuel injection
independent runner manifolds. In fact, Ford recommended using two of the
1400 CFM inline carbs on a Doug Nash fuel injection manifold for all out
351C drag racing efforts.
The carbs themselves used a lot of off-the-shelf Autolite 2 barrel carb
hardware. There were also calibration kits (part number D1ZX-9S549-AA)
and gasket kits (part number D1ZX-9502-AA). These were strictly race
carbs and were never equipped on any production vehicle. Early versions
didn't even have idle circuits, requiring a delicate throttle adjustment
just to get them to run @ 1500 rpm. Later versions were equipped with
idle circuits that apparently worked quite well. In a 1973 test conducted
by Ak Miller, a 351 Cleveland equipped with dual inline fours was tested
against an open plenum tunnel ram equipped with a pair of conventional
Holley 710 4 barrels. Low speed operation with the tunnel ram was termed
"very poor" and the engine didn't start to work until 5000 rpm. The same
engine equipped with an independent runner intake and a pair of the 1400
CFM Autolite inline fours faired much better. Peak horsepower matched the
tunnel ram but, with the inline carbs and independent runner intake, the
engine idled well at 600 rpm and pulled evenly across the rev range. Low
speed operation was termed "fantastic". Ford had great plans for the
inline carbs but like many of Ford's better ideas, the inline four died a
premature death when Ford pulled out of racing in the '70's.