According to Bunn's book Dodge Trucks (Crestline), Dodge made dual carb/exhaust setups for two of their inline 6 truck engines. The first one was for the 331/377 BIG six. There is a picture of this unit in the book. It was used in 4 ton trucks. Don't know about other sizes.
The other setup was for the premium 265 engine used in 2 1/2 ton trucks from 1953 to 1959. This unit is also a bolt on for the 251 engine. The 1953 265 with dual carb/exhaust was rated at 135 hp (the single carb version was rated at 120 hp). In 1959 the 265 dual carb version was rated at 141 hp.(130 hp with a single carb).
Chrysler also ran dual carb set ups on marine versions of these blocks.
