if he is running out of gear...the car will still et pretty close to what it had run previously but the mph will be down....in his case both are off.....lack of power or something not right
As for the gear choice, small blocks need gear for sure. I had that same cam in my old 340, shifted it at 7,200. When I bought my car it had a 4.30 gear in it which I changed out for a 4.10. It was a step backwards, it needed the gear, the launch was soft afterwords. It would get up into the rpms really quick with the 4.30 gear, even the small 5% change was noticeable.