I can't see cam alone adding ca. 130 horsepower. Cams only make the most of the other parts, and Shelby was already making an awful lot from those bits. The only engines I've seen with ~550HP have significant additions beginning with substantial improvements in displacement and breathing on top of an optimized cam. The original cam is only mild by present-day standards, not a lot of room for improvements. (Certainly not the kind of improvement that would be seen over an era street cam.)
I'm not saying you aren't being truthful, but I'd have to see documentation before accepting such a claim. It's just too easy to overstate results *and* the reasons for increases. A dyno sheet? Fine. But all too often, the claimant is forgetting about porting, port-matching, oversized valves, roller rockers, a little stroking...
