If you do a prefit with a barrel nut you will also have to inlet the stock for the nut unless you are installing the barreled action in a chassis or a stock with a large barrel channel. If you already have a decent stock on the rifle (not plastic) have a gunsmith rebarrel it to the caliber of...
Man I’m glad to see you hack this frame. I have the carrier frame from them without the shelf and have similar complaints. I used one of their large zip on duffles with two bat wings and a spider web of home brew 1” straps and buckles from the army surplus store to get me through this elk season...