You will be ahead of the game with a raised cam block if you're going to go 604 with a wedge head. With a standard spaced cam tunnel, you can't get any decent lift without fouling the rods with a 4.75 arm. Lift can be addressed by rocker arm ratio but that creates there own little problems. Better off deciding now, belt drive is a lot more expensive than non raised cam tunnel.
We've not ran bushed lifter bores and they're holding up fine. Our's is 580ci btw. Nice reliable, low maintenance 850 ish HP. 6700 shift. 7200 max rpm. see sig.
HTH's