The oil blowing out of the dipstick tube and breather is likely from "blow by", which is combustion pressure escaping past the piston rings. No oil pump, high volume or otherwise, will cause blow by. There are other possible issues with running a high volume pump with an Olds though, such as a stock oil pan getting sucked dry and all the oil being in the valve covers - not good!
Sounds like your engine aint in such great shape. I'd suggest doing a compression test.