harness questions

[Dougie360@aol.com]

i all, I'm a novice and am trying to understand the harness options.

1.  will the addition of a harness disqualify me from Stock?
2.  I don't want to do major mods in my car (like roll cages), and want to
keep my car in GS.  I believe that a Schroth type harness is the option. 
Anybody know a good source/supplier for this harness?  

thanks,
Doug