2.300" intake and 1.75" exhaust will fit the tunnel port heads. Valve spacing on a 427 head, tunnel port or medium or high riser, is 2.100". I agree with Brent though, I'm not sure it is necessary to go to a 2.300" valve to use the flow capacity of the intake ports.
Valve spacing on my SE and RE heads is smaller than the 427 spacing, at 2.050". This is so that it is easier to use the heads on a 390 stroker or 428.
The chamber in my SE and RE heads is better for flow than the tunnel port chamber I designed. The reason is that the valves are moved towards the intake side of the head, making them closer to the center of the bore with my SE and RE heads. This allows for a more gradual turn to the deck on those heads than is possible with the tunnel port design, or any FE design for that matter with the stock valve location.
Also, keeping the chamber small allows for decent compression with a flat top piston. So you won't need those extreme domes that are seen with factory tunnel port pistons.