I dont know if this will help your comparison between steel and aluminum but the semi I drive has a dd15 (detroit) that on a daily basis pulls around 80, 000lbs. Its just shy of 500 hp and just south of 2000 lbf of torque which it will generate in about 1.5 seconds from idle. First gear is 14.80, seventh is 2.45,
, and thats a mild 10 spd. Some L or LL trans get into the 20.oo. It has an aluminum drive shaft. Most semis do now.
I did drop one about a month ago, in my yard, backing into my parking spot at the end of the day. It failed at the u/joint on the diff end. Its about as thick as my thigh and you could easily carry it with one arm, so there is major weight savings to be had with aluminum.
I guess this doesnt apply to a sc application but if only to shed some light on how durable aluminum is. Our 2013 trucks, some delivered in 2014, are quickly approaching half a million miles, most over 400, 000 already. They run two shifts day and night by multiple drivers on the worst roads in some of the heaviest traffic in the country. They are dependable, but they are also not aftermarket produced or enginered.
That being said they do fail, they are designed to do so at certain parameters.
https://youtu.be/IEH-xRUaAos
Money no object?
Could always go carbon fiber?