28oz vs 50oz balancer..WHAT THE HECK?

I have a 72 351w. It has a 28oz imbalance damper. I bought a new chrome balancer listed for a 28oz imbalance. Double checked the p/n on it. It is the one listed for 28oz.
Heres the problem..or not a problem. I am running underdrives and a serp belt.
Everything I read says I need a crank pulley spacer to make the belt line up. I DON'T! It lines up perfectly. The balancer looks differant from my 28oz factory unit, but I did the research, it should work. WHAT THE HELL?

moonenn3186 said:

You generally only need the .875" spacer if you are running one of the stock 302/351 28 ox 4 bolt balancers. Most all aftermarket ones are the correct diameter. I was told the same thing as you - I bought a spacer from Ford for $35.00. I of course did not need it for my aftermarket balancer and now I can 't sell the damn thing for a plug nickel.

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Well, thats 2 of us. I did thr reasearch. My new one should work. I have a spacer on the way from a guy on ebay. Now I have one too. Oh well, I'd sooner pay the 25 bucks and hang it on the wall, than hang it on my motor. Thanks for the input, I just needed reassured.