[davepl]

Put it this way - when you stand on the throttle, the RPM will flash to some point, like 1500 with a stock converter or 2500 with an aftermarket, and you want your cam to be somewhere at least close to its working range.

If your cam works at 2500, and most stock LS cams sure would, then you don't need a converter. But if your cam is sleepy until 3500, then yeah, you do (though I'd change the cam in that case!)