Here is an Ebay auction for a used 66 radio block off plate by Ebay member "gtmotorsports66 " with a starting bid of $95.00:
Here up for auction is a very nice in used condition 1966 Mustang, Shelby, 66 Trans Am radio delete block off plate in black. The Ford engineering casting number is C6ZB-6504371-AW and with the Fomoco logo. It has two 1/4 in. screw studs approx.1 in. long installed on each side possibly because the original plastic metal nut's screw threads on were stripped off at one time some how but this being replaced still works perfectly as it was designed to. The shipping is for only in the lower 48 USA State's. Good Luck & Happy Bidding !!