[Large Arbor]

Glen,

I think the answer is many reasons. They are:

1) drive ability (lesser cam needed), hydraulics and factory rockers are still good.
2) parts availability
3) no visible difference except in performance
4) sometimes the additional HP does get called on
5) you can street it without spinning the tires (a lot)
6) The originals were not far off 500 HP with worse tires, suspension, etc.
7) the newer tires, 5 speeds, reward end ratios, all provide support for the higher horsepower.

I did not select my engine, simply bought the car shortly after the build. The lightweight aluminum was a plus to the hp and ERA car.

Phil