I’ll first start by saying, I messed up. I had 2x Interarms Magnum (so I thought) actions. I purchased these actions with stocks, reloading equipment and ammo for 375 H&H and 458 Win mag. I sent out of the actions to have rebarreled to 375H&H. When I got it back, I put together the rifle and found it was NOT a magnum length action. I spent a pretty good amount of money to have this rebarreled.
I have 2 options:
1) Open up the action slightly to accept the 375 H&H and get the correct bottom metal. Is this is doable?
2) Buy a 375 H&H Mark X locally for $500 and swap the barrel + bolt if this is even do able. I can recoup the cost by selling the old action and other parts. I’d prefer not to do this because I also had my action ceracoated.

What does the campfire recommend?