Why don't you start with the base 302 windsor engine,an import from the states,they seem to be cheaper then the Ausssie units.Swap the crossmember over to the EB unit.Then use one of the many stroker cranks from SVO to are other brands found in most Mustang books.Holley and Offenhouser are some.Not quite sure if either of these supply cranks but I know for shore they have there own bolt on kits which definatley produce the goods.Most kits include heads,cam and manifold and possible extractors and even bigger throttle bodies up to 80mm I think.
The Yanks are made crazzy with there Ford's especially the Mustang.I'll have to find this Mustang book I have,with one very quick street stang on the cover running into the 10's I think with out bottom end mods.This is of course the 5.4 L.Its a shame there is not more Falcons V8's cruzzing the streets with some American parts under there bonnets.Most Ford dealerships will be able to get you a SVO cataloge with all the prices and parts unthinkable in them.You can even get a race prepped short motor.
Here are some sites might be worth looking up.
( 347 ci stroker,389ci stroker kits)
Hope these help.