Why stainless? Brass and Thermoplastic work well on the CO2 side. I am an advocate of all things being stainless, but I run Brass Industrial QD's and Thermoplastic QD's for the gas side. I get them from my company, Parker, but you can get the Colder Products at any LHBS or Northern Brewer or any other online shop. Use the gas line and barb fittings. I use a brass manifold for the 5 keg splitter to the thermoplastic QD's.http://www.northernbrewer.com/shop/cpc- ... -barb.html
Use standard gas line then, 1/4". You may need to go to a Parker or Colder distributor to get teh male and femal pipe versions if you want to run a manifold. FYI.