Im looking at doing a 2 stage upgrade and was wondering what sort of power increase i could expect, atm it is 100% stock.

First stage would be GT40 heads, explorer manifold, full exhaust and electronic shift kit.
What sort of increase could i expect from that?

Second stage would be a stroker kit(347 or351), increase compression, bigger injectors(if needed), cam, remap ecu and modify trans (if needed).
what sort of power could be expected from this?

Figures are varied from source to source, a Mustang forum in US that i found said that just the Explorer alone was good for 15kw but ask ten people you'll get ten different answers, in case you're interested i've got a real tidy Explorer manifold, polished 75mm Ford Racing throttle body and matching EGR, phenolic spacer for between top and bottom halves of manifold that i've decided not to use as i should concentrate on my ZD Fairlane project. PM me if you're interested.