i dont think thats entirely true..
my eb2 xr8 didnt have a speed limiter and had a steel tailshaft!

i mean maybe the e series had crap quallity tailshafts?

if you look back the old gt falcons did well over 220kmph and all had one piece steel tailshafts and they were not speed limited.
the same goes for the old valiants they would do well over 220kmph aswell and they had tailshafts that were like tooth pics..lol

but the amount of power and speed the older muscle cars were making they needed something strong..
i agree the alloy one is lighter and is strong enough for the power of the e series..
but its not stronger than the steel one!
otherwise all race cars would be using them..