340 6 pack cam???

mopar purple cam P4120231 284/284 dur 484/484 lift 2600/6000 rpm

that is what is in my 340 with somewhat similar specs but with mildly ported J heads. This cam was recommended to use 4.10 rear

The 508 cam is just a bit much for the street from what i was told, but i have yet to run the engine.