Harmonic balancer help

I got in touch with the manufacturers engineer Ed Lions. They were very helpful and gave me his cell number because he was at a car show in Florida.
Locomotion, you are correct and I thank you for saying something about it.
This will fit all smallblocks EXCEPT the external balanced 340 because it has a different size weight (which this company doesn't make) just like you said.

I called Wes at Mancini to explain the situation to him and he was extremely apologetic.

Thanks man, you saved me some huge and expensive hassles down the road and kept me from passing on some incorrect information.

On a good note, I have a 360 sitting in the corner and I can use it on that.:-D