+1 on Kirby for building your rifle. I currently have two 338 Khan's and a 510 AM he has built. They are all excellent shooting rifles, you can't go wrong getting Kirby to do your build.
I also have a 338 AM in the shop as we speak. I hope Kirby finishes it up a little early for hunting season this fall, but probably will get it a little later in the winter. As one other post said, I would recommend just contacting Kirby and let him put the build specs together. You can fine tune anything you want to change. The Raptor action will not work for the 338 or 375 AM. I suspect your list from kirby will look something like this:
32" Lilja barrel
5 port Pain Killer brake
McMillan A5 stock with adjustable cheek piece
NF rail, rings and scope
The rifle will weight in at around 18 lbs give or take a pound or two. There is really not much to mess with from Kirby's standard build list........ Just pick your stock color, the finish for the metal, send him a check and sit and be prepared to wait impatiently for 12 months.