ATI-917270 7 1/2od steel
ATI-917268 7 1/2od alum.
ATI-917271 6 3/4od alum.
ATI-917272 6 3/4od alum.

Don't really know which one to get. I think stock od is 6 3/4, but not postive on that. Which one is everyone using. Going to order this today.

 

Well I ran into the most unusual things trying to investigate this question. First I can say the stock pulley I measured from the engine I rebuilt was 7.5". The Fluidamper I have is 7.5". The recommended ATI diameter from Summit (according to their catalog) is 7.5". But when you try to pull up the 917268 or the 917270 on their website, they won't come up.

What else is strange is some other websites recommend the 6.75" but that is a 10% underdrive and may not work with the stock length belt and tensioner.

The other wierd thing is Jeg's doesn't even carry the ATI unit.

I would say to stick with the 917268 It's a good choice and since you're in PA, it won't rattle your teeth out and take forever to warm up like my Fluidamper.

By the way I'm originally from Willingboro, NJ. It's good to talk to someone from home.

Take care