[Christ]

the 3-stage Vtec has 2 solenoids, which are interchangeable from other D-series Vtec engines, so that's covered.

The bottom end is simple, as well, since it matches that of just about any other D-series engine.

The cam, well, have fun with that one, no idea.

The valves and lifters would be the same as many other engines, as well. The only parts you'd really have to worry about are the actual Vtec activation motion assemblies (can't think of their names right now)

You could probably get another head for less than the price of a rebuild, should you need any parts, so it's not really worth it to worry about "maintenance" in that scope.

The only thing you'd need on top of what you already have is the ECU that controls the 3-stage Vtec, but you could easily set up the system on switches or activation, etc. so you could control it manually, and stay in the first stage for the whole drive, which kind of kills the idea of using the 3-stage Vtec in the first place.

The other thing is that the 3 stage engine doesn't have lean-burn, to my knowledge, and the lean burn ECU doesn't support 3 stage. You'd have to overcome that boundary as well.