Might be worth a call to a dealer to get them to check on their parts CD as this contains all the schematics for all years / models ... if only I could get my hands on one of them
I have .pdfs of the parts lists for many Ducati models and the idler pin is universal for all of them from a '94 900ss to '03 ST4s including the 748, 916 and 996 series and presumably all of the Monsters, but NOT the Testastretta engines. So Antony's 748 one will fit.
As per U2U to Dibble I will check when I get home to make sure there is one in among all the 748 engine parts. If so I was hoping to get it to Everton tonight but judging by the couple of Texts he has just sent he would prefer to meet up on Thursday evening. Slight problem there as I may be at Donington by then.