This is common sense. Alum!!! period. Factory cars come with Alum now and even carbon Fiber..
Your making how much power? 300hp 500hp 1200hp, How about Promod cars that make 2500hp? Wonder if theirs is Alum? YES
Alum isnt the question here, Its how big DIA. the Shaft is.
Anything over 600hp go with a 4" Dia.
It all comes down to "do they know how to fab a shaft properly"