My '75 280z engine looks like leaking oil from rear crankshaft oil seal.
I'm about to order the oil seal part,
http://www.carpartsmanual.com/datsuns30/Datsun-Z-Index/Engine-280Z/Cylinder-Block
Parts number is 12279-R4601 SEAL-OIL CRANKSHAFT
It cost $40-$50
I saw someone is using 240SX part# 12279-5L310
It only cost around $10.
http://www.pitroad-ts.com/tuning-page/tsuchiya240.htm
I wonder those are interchangeable?