Keeping the bore close to standard leaves plenty of material in the bore for rebuilds down the track. leaving the stroke standard means you can run the standard rods.
Good Hp is made by getting the engine to shift alot of air. It can be done with capacity, but the top end will still be the limiting factor.
It becomes a Cost/Hp balance. Personally, for the bottom end i`d go A15, standard crank, rods(closed and honed with new arp bolts)and flat top cast pistons 76.5mm.
The H98 head is a good one and the standard valve sizes are big enough with the right cam to about 7500rpm. The Wade 140 will fall over before that but is good on the street. You will probably want more duration on the cam for track use.
Your idea of the twin 40`s and elctronic Ign is good. You will have to keep your exhaust fairly open if you want the best from a cam with a bit of overlap.

The A14 and A15 blocks are the same from what i can tell. So the A15 crank, rods and pistons will go straight into the A14 Block. It might be less problems for rego. I cant see any other reason for doing it tho.

Remember to send a set of followers to Wade to be resurfaced when you get a cam done. Its only about $30 to get them done.