I would probably take a Kimber Talkeetna and rebarrel to 416RM or a stainless Winchester Model 70 rebarreled to 404Jeffery.
I built a .404J on a M-70 RUM action. Less modification that way, just open the bolt face.
This one in a Echols Legend stock that I steel bedded and freefloated. Williams bottom metal fit perfectly, D'Arcy's inletting is perfect.
DF