RE: 375 H&H Action Length...
I believe youd have to pick either the barrel or the action, a .375 h&h is too long for a .30-06 action, the .375 ruger would work in a .30-06 action.
If I had to pick the barrel or the action, I'd choose the action, and maybe build a .375 ruger.....or just use the action on some other big game gun/rifle build. Maybe a .338 win mag?
though if the deal is on the barrel, not the action, you can get the barrel and look for a model 70 action ready for a .375, though I think the word is out that the win model 70 action is awesome and great for big guns, ie the .375h&h, so finding one at a deal would be tough, now you can prob buy a new model 70 action.....though again youre prob paying a premium for that.