If the engine block is the same (PH15 and D15 are essentially the same block), there should be no issue with using other flavors of VTEC. Yes it is different but the difference is only restricted to the cylinder head (i.e. the very top of the engine) because almost every VTEC iteration is just a valvetrain technology. As mentioned it has nothing to do with mounting.

I'm not sure the 3-stage VTEC is restricted to just D15s though. The ES Civics had this stock and I think they used PH16 engine blocks which I think were based off D16s or D17s. Correct me if I'm wrong.