Steve,
Try a search on Campi wheels. There are all kind of articles on cleaning, stress releiving and finishing the wheels.
I think sandblasting is too agressive for Mag wheels. Media blast or manual cleaning will be best. Search around lot of good suff. Use the find key
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.