440 Camshaft recommendations for up to 6-6,500 rpm?

Ricks70Duster340 said
The factory rating was quite underrated. The stock 440 HP made closer to 425, and the 6 pack 450. Any engine can benefit from breathing improvements!

I've not seen unbiased dyno numbers on the big blocks, but there have been plenty on the 340 and they were pretty close to their advertised power.