Here's what I used:
Krylon (Metallics) - 1403 Dull Aluminum
It's tough to find be I picked it up at O'Reilly's.
Check out this link (post #185) for an after shot with the paint on the wheels:
http://67-72chevytrucks.com/vboard/s...k+slate&page=8
Let us know if you end up using something difference, and your experiences with that product.