This is called a counterbore. Try WLFuller.com. Order it without spurs 0and with an I.D. to match the nominal diameter of your hole. Use a bit of straight rod or a drill bit chucked into the drill motor upside down as the mandrel. WL Fuller is a GREAT resource, as is McMaster-Carr.
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.