318 power?

If the CR is accurate, I think it could get close to 400hp...... if......... the valvetrain behaves itself and allows the engine to achieve peak power at the natural point where the combo of parts maxes itself out.
Instead of a situation where the curve is still climbing....... then the valvetrain gets unsettled and the party is over.

The cam and heads are big enough to allow the peak to occur well above 6k........ if the valvetrain can keep up.