Is the oil pump ok? If it is then most likely the oil feed lines are plugged,maybe from sludge in the crankcase after sitting for 3 years.Even an oil change doesn't remove sludge.Maybe after the rebuild the rebuilder didn't run a brush through the oil feed lines in the block and head and metal shavings from machining were left behind. You need to pull the pan,side cover and head and start cleaning.
