lol i aint skeert of aluminum. just dont think it's worth the money sometimes. alum heads and intake definitely. pistons of course. water pump sure. aluminum hood for a body would be awesome if someone would make it (i'm thinking about getting an aluminum hood fabricated next year; take out the springs, put hinges in and use stock latch up front. use a hood prop instead of a spring loaded hood)
flywheel/driveshaft maybe if the price is right.
rods probably not. there is a durability factor too.