It's been a long time since I owned a 2000cs so don't know if this would work, but there's an M3 S14 rebuilt engine on eBay. Might be a good replacement for a tired engine if this is a viable drop-in.
No affiliation, etc.
http://cgi.ebay.com/ebaymotors/BMW-...p5197Q2em7QQcategoryZ33615QQitemZ290545454056
No affiliation, etc.
http://cgi.ebay.com/ebaymotors/BMW-...p5197Q2em7QQcategoryZ33615QQitemZ290545454056