Dottore (and others)
Go here:
http://slmarket.com/news/I am a subscriber and just received--on Tuesday--the latest issue which contains an astoundingly detailed price guide for SL's, updated to today.
SL's in this guide are divided into 6 conditions (1=Trailer Queen 100pt show car; 6=parts car) and things such as the ZF are accounted for in price by a panel of experts whose names are familiar to many of us.
Armed with this information, and someone who knows the cars, you can evaluate the condition of each, the options, and see where the asking prices are.
If you plan on investing the time and money in looking at and getting a W113, best to arm yourself with as much information as possible.
Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America