Re: mkIII 22/45 question
Two things: One, the RP (replaceable grip) model isn't on the handgun roster so its only available as a FTF if you can find one. Two, the upper is the registered component of a 22/45 so it has to be on the handgun roster. Tac Sol does not have "approved" uppers that are on the roster so again its only available via FTF, if you can find one.
That said, the 22/45 is a great little pistol. My mistake was buying one then hanging out on Rimfirecentral.com. There are tons of mods to be done if you like to make it even better. The thread valise pointed out above is a great place to start.