Greg Bender
http://www.thisoldtractor.com/gtbender
I extracted the information about the five speed spacer dimensions from Ray Hale off of the old Topica Loopframe_Guzzi news group (which has now moved to Yahoo!).
These are the aluminum spacers that fit on either side of the transmission and through which the large transmission mounting bolt with the 19 mm head is fitted.
On four speed transmissions, the left side spacer is 57 mm long and the right side spacer is 42 mm long.
On five speed transmissions, both the left and right side spacers are 57 mm long.