I'd utilize hawkins/GrayOps 2.985 internal mags with a hawkins/GrayOps hunter dbm, or a cfe5 3.00 internal centerfeed box with a m5 oberndorf bdl bottom metal(allows 3rds down). You'd likely need to mod the bolt stop and the bottom of the action to get the magazine up inside the action.
Starting with a rem700 action, the need for blue printing and extraction timing, plus the needed cuts to the underside for long mag feeding and bolt stop mod, is a lot of money/work when there are options available.