[Excaliber]

425 horse was the accepted "politically correct" number widely used, often quoted, written in books, acknowledged by NASCAR and often seen today in various reference manuals. It was never officially confirmed or denied by Ford.

Many believe the center oilers of '63 and '64 were making a true 500 horse, "stock", as delivered in a Thunderbolt anyone could buy at their local Ford dealer. That 500 horse number is supported by 1/4 mile calculators using known Thunderbolt ET, trap speeds, weight, gear ratio's and tire size.

In 1965 and later, with the new side oiler, it is estimated some T-Bolts were making close to 650 horse, all though, not "stock" at that point. But using parts available at the time.

Then along came the tunnel ports and the SOHC, either of which I suspect will flow more air than a Stage 3 Edelbrock head worked over by the masters. But I could be wrong about that, perhaps they are equal in that regard?