Advice needed

The problem with the words "Bigger cam" is do you mean more lift or duration.

Duration dictates RPM band of which the engine operates in.

Lift has a direct impact on HP, but how much lift the head can handle is in question.

I'm not sure I will ask him but I would think he means a little more lift & more duration as well.
The guy who done my heads said that 525 to 535 lift is all the heads can handle any more & there is no benifit.

He has since retired so I have gone to a new engine shop & they recon that I will benifit from a bigger cam. I just don't understand how if the cam I have is able to flow all the heads are able to how fitting a bigger cam will help.

The guy at the engine shop is aiming for 550HP out of the set up he is building for me.

Cheers Oz