Anti-roll bar spec

[spotontheroad]

Can anyone let me know the spec of the metal used to make an anti roll bar. I'm quite capable of making an anti roll bar set up but just need to know what spec (metal type as opposed to bar diameter) bar to order from the steel stockholders.
Also any respectable/reliable sources for rear coil overs or coil over kits would be much appreciated.
Many thanks in advance

Keith