I'll take a shot-
Bravo One- Mercs standard big block outdrive
Bravo XZ- Beefed up Bravo
Bravo XR- XZ with straight cut gears; used for racing in the factory classes
SSM III- Super Speed Master racing unit; not used much anymore; not available with current packages
SSM V- same as the SSM III, but 6" shorter
Number 6 Dry Sump- The beefiest of all the drives; "dry sump" refers to how the oil is sprayed onto the gears, instead of bathed (less HP loss); needs a separate transmission, very heavy and very expensive.
A Bravo 1X is a diesel drive, which is a beefed up Bravo for the extra torque.
An extension box is a billet housing that moves the drive back off the transom. The idea is more setback = more speed.
Hope that helps.
[ August 13, 2002, 08:49 PM: Message edited by: Havasu Hangin' ]