Hey Mike, you mention maybe the only choice is the 5.4 Ltr from the falcon, and you may well be right.
However, I wonder, if one used say a 5Ltr from another approved specialist manufacturer like Roaring 40's. They use a recammed crate 302 with a 4 barrel Throttle body and Motec ecu. I understand they have approval for that motor.
Not sure, but that avenue may well prove the way to go for an approved engine.
Now, once registered, it may be that the crank and rods get damaged and have to be replaced, together with the cam...damn what a bummer.
.
Would be a first class pain too if the block got damaged and one had to get a dart block.
Les