Unfortunately, "best" and "cheapest" are usually mutually exclusive terms. But for the money, Mustangs Unlimited has solid 1" blocks
http://www.mustangsunlimited.com/itemdy00.asp?T1=LB1X+01
You might have to buy longer U bolts and I don't know if they're included in the deal. NPD also sells 1" lowering blocks but they're not solid but U bolts are included, all for about $30. Good luck...