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The Hughes rockers I recommended are advertised to work on iron heads only. They might can be made to work on aluminum heads like Tony says, but they are not advertised to. They are nice pieces though.

I also really like the little Comp cast steel roller tip only rockers. They are nice. Very affordable too. I just put them on my little Ford motor.

These:

http://www.summitracing.com/parts/cca-rp1416-16/overview/

And you need this too:

http://www.summitracing.com/parts/crn-36655-16/overview/

It's a really nice little kit. I put that and the Comp rockers on my 302. You also need to make sure to get the right length pushrod. Sometimes the stock ones will work, sometimes not. I needed longer ones.