Muchmore Trucking

Hey new to this forum.. ive got a 1980 r model with a 237.. I have a leak from behind the injector pump.. hard to say if its fuel or oil? after truck sits over night, it takes some cranking to get it going the next Moring. once its running it runs mint all day.. obviously losing prime... just looking for some help. also is this a 2 or 4 valve truck? Truck uses 1 gallon of oil a week. Also getting oil in air tank.. any help would be greatly appreciated