ACC does appear to be the designation for accessory codes.

A list in which "WV" does not appear but shows that "ACC" does refer to "Accessories".

http://www.348-409.com/acc1.html

An ebay auction in which the 1960 Impala is advertised as having the ACC code WV.

http://cgi.ebay.com/ebaymotors/ws/e...viewitem=&item=150082352708&rd=1

Finally, a resource book for 1960 Chevys that has ACC codes on page 2 according to the index of the book. (You can view the index but not page 2 from the Amazon site)

http://www.amazon.com/gp/product/08...reative=9325&creativeASIN=0837609364

Perhaps you could browse this book at your local library or bookstore and nail down your mystery letters.

"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson