Have the 5.7 blocks sonic checked to see what they will take for an overbore. I have heard of some thick enough to go 4.06!
As far as valve shrouding by running Apache heads on a 5.7, the pinch spot next to the cylinder wall is the weakest flowing portion of the port. On top of that the valves move away from the cylinderwall as they lift off the seat. Lastly, a slight notch could be ground into the block ala old school wedge engines, if you like to worry about it.