525i-12v and 24v engine prod. dates?

["Rob" <motor@xxxxxxxxxxxxx>]

    I'm looking at buying an '89 or '90 E34 525i but I'm a little confused
as to exactly when they went from the 12valve (M30?) engine to the 24valve
M50.
Was there an exact prodution date change or did they just put in whatever
was available on that day?  I really want the M50 equipped car !
  Also, what other changes did they make from '89-'90??


TIA
Rob
motor@domain.elided

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