The P-14 is a fine action to make a 375 on, but like with everything else, the quality is variable depending on who did the work, how well it's done, and what parts he used.
In the better examples, they make a very fine rifle. I have a copy of an old Holland and Holland ad that shows a 300 Super (300 H&H) made on one. They were good enough for H&H. So if the work's good, you will be pleased