narrow case crank ?

[miken5678]

http://cgi.ebay.com/ebaymotors/ws/eBayI ... MEWAX%3AIT

noting the difference atleast based on this ebay auction it is considerably different than my monza crank. The only benefits I can think of are lower recip mass and possible higher/easier revs and better balancing of the motor however I also realize the monza wasnt gifted many improvements w larger valves etc so maybe this presents a great improvement.