I have few Ducati shocks laying around (900 SS, 996 S and 1198 S) none will work as the reservoir is positioned differently and interferes with the frame or some other issue, I already tried....
What seems to be best fit for MC18 is the 1994 CBR 600 F2, it's a one year only here in US as '93 has non-servicable shock and '95 has a different dimensions. '94 However has remote reservoir, adjustable compression and rebound and spring rate is almost same as MC18 (little higher which is actually better considering I'm a bit larger than typical Japanese teenager the NSR was intended for) The only mod you have to do is top mount has to be shaved from 27mm wide to 25mm and drilled from 10 to 12mm
By the way, every 748-916-996-998 bike has the same spec shock, only difference is the spring rate, more spring for 2 passenger.
Sachs came on entry level bikes, Showa mid-level and Ohlins top shelf
OK, here are some pics to illustrate
900SS shock with clearance issues
916 style shock (this one from 996)
and here is the problem with 848-1098-1198 style damper, wheel adjusted all the way back. This is an 18" wheel, I don't have a 17 to check clearance.
Another problem is that NSR linkage ratio is much lower than Ducati so NSR uses roughly 750 pond spring while Ducati is in 450 pond category which is a significant difference requiring complete re-valving