Yes, we still offer southpaw uppers in a few configurations, and rifles can be upgraded to southpaw configurations using the "Rifle Upgrades" section when ordering a rifle.
If you needed an immediate response, you should contact me at firstname.lastname@example.org or (763)261-5600. As I've posted many times before, I reply on these boards WHEN I HAVE TIME. I give priority to direct e-mails and phone calls.
bolts and uppers are not machined together, nor are they machined at the same time, nor are they machined by the same shop, nor are the raw materials the same, so I don't know how this applies. Of course we don't make 500 receivers and 200 bolts, that would be absurd.