[blykins]

Changing the heads would be the biggest jump for you right now. Even a ported E7 head probably won't flow 200 cfm. You can get an immediate 75-100 hp bump by changing to a good set of AFR heads with stud mounted roller rockers.

If you stay EFI, ditch the stock 5.0 upper/lower intakes and get a good Trick Flow intake setup, matched for the application.

With those two upgrades, you'll be very surprised.

Without upgrading to some good rods, I probably wouldn't take it any further than that.