As you all know I spun a Big end bearing on my BBO. I bought another engine from a guy about a year ago but never collected it. A couple of days ago I fetched it and found the folowing.
Block casting 396021 FA
Engine nr : L5E015594 - marine/Irragation engine
He imported the engine as a spare when they were doing speed skiing in the 1970's -80's. The engine never ran in a boat, only on a test bench. Over the years he sold some of the parts, carb, alternator etc.
The heads are KA - still virgin
Crank, pistons etc STD with the factory GM marked bearings.
The only difference I can see is on the Oil returns on the block. (Pics attached) Red block is "F" and Blue block is the "FA"