Otis,
The exact number is not known, nor is the logic to who got them....but indeed, the factory did have Campagnolo cast up aluminum wheels for these cars..... Speculation is somewhere around 20 cars......WAG here.... NORMAL wheels are magnesium.
The first 25 or so Mangustas did come with HiPo 289 engines. Exact count is TBD as factory didn't release this sort of production info. There may be a "notebook" that could confirm, but not sure if the owner is sharing freely......!
Ford was indeed still making 289HIPO engines, just not for production cars! The parts division was still receiving them! I was able to check GOose #4 out years ago, pre digital camera...and I can't find my film pictures...DOH!...... and that car had a true 289HPO engine with casting dates on the intake, heads, distributor, and carb, that were all early 1968 dates IIRC. The dates were similar to the dates in the window glass also! This squashed the idea that the cars were being produced (enmass) in 1967.... nope!
The 289HP cars had a couple of unique 6 bolt bellhousings for the smaller diameter flywheels, and "many" bolt jackshaft holders! I forget what all else was different..... everything else should have pretty much been carried over to the cheaper 302-4V Cougar/Fairlane/Mustang engine.
Cheers!
Steve
PS: Not sure the BAT crowd will bring a proper price for this car....but then again, it would seem that buyers have abandoned CraigsList and are paying up for BAT cars??? 
POS cars almost criminally over sold, have brought more than the $325 number. This car deserves the new $400K mark! What's a missing screw!? Probably vibrated out due to being driven!!!!