Good luck getting the 'missing' 50-75 hp by advancing the cam 4*.
You usually have to retard a cam [ not advance ] to gain top end hp. And I doubt retarding the cam will pick up 50+ hp.
I commented earlier in this thread that I thought the HP was about right for the combo. You might reach your goal with a more 'optimistic' dyno.
You can get into the realms of idiocy with this stuff. I know a bloke who claims installing a 1" carb spacer to a T2 intake gave a 102 HP increase........
