You may as well go the 351W as it will require the exact same work to install as the 302W would. But with the 351 youve a stronger block and a larger potential of capacity increase, you can go as far as 427Ci on the 351W block.
The only difference would be possibly a hole in the bonnet to clear the intake manifold, and custom made exhaust manifolds. (the standard upper F150 manifold wont clear without bonnet mods, but possible the upper GT40 may clear)
Stock power was only 150Kw/420Nm, but with decent heads, cam, intake etc 300Kw/600Nm is easy
Rego may require chassis mods, bigger brakes etc though....