From
http://www.bikeboy.org/duccapacities.html Some notes for component swapping – not an absolute list by any means.
The cylinder stud spacing variations are:
‘Small blocks’ (small 2v),
‘Large blocks’ (900/906/907, ST2 and 748/851/888/916),
‘996’ (996, ST4S, S4R, 998/999/1000ds/ST3)’
‘Large Testastretta’ (104mm bore 998R/999R, 1098, 1198).
Swapping cylinders between the different variations is not possible. Well, not easily. The holes in the cases for the cylinder spigots to go into also vary.