In the old forum I posted a pic of two Shelbys with the C5OZ horned forks and got no feedback and made an assumption on applicability.
It appears finding a picture of these things is difficult as many people post on ebay that they have a HiPo fork, when instead all they have is a fork 12" long. I believe the second pic I posted (with the hole in the cone) is of another erroneous ebay posting.
I'm really only posting pics to get feedback (like the OP) on what one really looks like. I need one too. With all of the issues people seem to have with posting pictures I'll keep at this until somebody says, "Yeah, that's the one."
A bit off topic is one of length measurements. The only two lengths that matter are from the fulcrum to the TO fork and from the fulcrum to the cone.
The C5OZ is 4.0" and 5.125" respectively for a ratio of 1.28:1.
A 12" fork I have here that closely resembles a HiPo fork is 4.0" and 6.75" respectively for a ratio of 1.68:1.
The added leverage of the longer fork gives you added leverage on the bigger clutch (compared to the std 289) decreasing pedal effort. And giving longer life to your Z bar.
Anyway, here is the latest pic I found of a purported 289 HiPo clutch fork:
[edit for grammar]