Sounds like a standard M30B34 engine, as fitted to 5,6&7 series cars from 1982 onwards. Can't imagine it's particularly rare. The team on bigcoupe.com might know more, as it's their era of M30
The M90 displaces 3453cc, as opposed to 3430 for the M30B34 and is rarer. The M90 came with either l-jet (and old style dizzy), or with early motronic (with the dizzy fitted direct to the front of the head)
The M90 displaces 3453cc, as opposed to 3430 for the M30B34 and is rarer. The M90 came with either l-jet (and old style dizzy), or with early motronic (with the dizzy fitted direct to the front of the head)