my 66 ford 4 dr custom with factory 289 2bbl dual exaust and 3 spd standard gets really good gas milege close mid 20s
i dont know what my rear gears are but 1900 rpm is about 60 mph .
you should do better with the 5 spd
4t is 1 to 1 like high in the 3 spd
my 3 spd just barly cuts it as the rear gears are too high. 1st is hard on the clutch.
i personaly am not a real believer in the big holley 2 bbls for gas milege.
you should do better with a nice small 4bbl
i know better mpg is possible for ya.