It's just an upper and a mag change, no big deal. I'm betting you can mod your own mags easily too with a strip of wood, some epoxy, and a saw.
I was going to buy a barrel from Satern (was like $200 and in-stock a while back). Brass is the biggie for me, I thought if 45Raptor dot com was out of it maybe I could get it directly from Starline. I'm sure it could be made from .308 brass but you'd have to ream it it out or something. PSA has the cheapest AR-10 stuff I've been able to find, even when all the box stores were having blowout sales on AR-10 stuff a month or two ago. I kinda got distracted by subsonic stuff, so the .458 SOCom looked mighty fine for a while but I don't really need one. The 45 Raptor would be a pig killing machine and have at least a 200-yard range, and THAT would come in very handy from time to time.