How much of a mechanical improvement is the 3306PC engine with the sleeve metering pump over the 333C engine with the scroll pump? I'm sure there are probably other differences besides the injection pump but that's why I'm asking if there is a better one to have. I've got an early 70s D5 with the D333C and I'm not happy about having a crankcase full of fuel among other issues and was thinking of trading her out for a few years newer and better condition D5 or D6C.