Sheet aluminum for polishing

[jlcustomz]

I,m getting ready to start a custom alum crossram intake project.http://ls1tech.com/forums/generation...gn-intake.html
I,ve done several raw fabrication projects from #316 stainless or various aluminum that i,ve fully polished. I already have a bit of .063 # 3003 h-14 alum sheet & a little 6061 plate. I figure for the runners on this intake, I,ll probably 2pc hammerform & tig weld from sheetmetal.Possibly samemethod for most of my 2 into 1 plenum setup.
My question :: is 3003 decent for polishing & holding a shine or should I look for another grade of alum. Also is .063 probably thick enough for my intake or should I consider thicker. Not everyday questions, I know.
By the way, anyone who appreciates handformed alum should check out my bedcover in the photobucket link. Learned to weld alum on that project.
http://s1094.photobucket.com/profile/jlcustomz1