MGB engine identification

["Larry Hoy" <larryhoy@prodigy.net>]

What is the best way to identify the "vintage" of an MGB
engine that has no ID plate.  This is an earlier engine; the
block is machined for a generator, not alternator and it is
a "pre-smog" setup.  I really would like to know if it is a
five main or three main engine.  It presently is in a 1964
car and is running.  I know that the 1964's came with a
three main but this may not be the original engine.

Any help would be appreciated.

Larry Hoy
http://pages.prodigy.net/larryhoy/