Mooso, "ten under" means the crank was reground to ten thousandths of an inch under it's original diameter. This is pretty common when rebuilding the bottom end with new bearings. It just cleans up the surfaces to a like new bearing surface. I don't believe there is any performance gain(others may know better).
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.