I was curious to know what the difference is between the standard seat belts and the optional deluxe seatbelts. Thanks for the help!

Standard belts have a plastic covered buckle, deluxe belts have a stainless buckle (that's for '68, pretty sure all the other years are the same).
Deluxe belts- http://cgi.ebay.com/ebaymotors/68-Chevelle-Deluxe-GTO-Black-Seat-Belts-442-GTO-1968_W0QQcmdZViewItemQQcategoryZ42612QQihZ013QQite mZ230222875504QQrdZ1QQsspagenameZWDVW
Standard belts- http://cgi.ebay.com/ebaymotors/69-70-Chevelle-Black-GTO-Nova-Seat-Belts-442-GTO-68_W0QQcmdZViewItemQQcategoryZ42612QQihZ016QQitemZ 260211863371QQrdZ1QQsspagenameZWDVW
BillL

Also the deluxe retractors have an inertia lock.

The contents of the Deluxe Seat Belts can vary, depending on the year.

Prior to '67 the Deluxe Belts gave you retractors where there were none. Special chrome buckles were also included. I believe ;) that through 1969 all belts were color-keyed to the interior, and that after 1969 only the Deluxe Belts were color keyed.

Steering wheels and columns were generally color-keyed on all cars except the SS from '70-on. After 1971 steering wheels and columns were black, but if you ordered Deluxe Belts you also got a color-keyed steering wheel & column (I still may be over-generalizing, but you get the jist of it).