The clifford intake with some injector bosses drilled for 6 injectors, a custom fuel rail (
www.rossmachineracing.com), a modded carb for the throttle body to control air, Megasquirt with the MSnSE code, and you have a cool little L6 engine. Could also make a barrel manifold with a single throttle body on the end, and 6 injectors would be a good way to go.
The new L6 engine GM makes is not anywhere near compatible with your current configuration. The Vortec 4200 is a completely different animal. Still very, very cool. I think in the next 5 years it will be a candidate for swaps in hot rods and customs. With VVT and sequential fuel injection, it would be a very efficient engine for mileage, and the off road GM guys are already making 450+ HP with them while still keeping the EFI. There isn't much available for aftermarket goodies or controllers for them yet though.