A shortened stock really takes a lot of the value away. Even a good modification like a crossbolt through a known weak spot for a 375 H&H stock, reduces the value as well. However, every rifle and configuration is different and value is adjusted depending on such... I have a great example on hand right now. It's a hard as hell to find montecarlo stock for a 375H&H. My smith put a crossbolt through the stock in between the trigger mortise and mag well. This is a known weak spot and you can expect failure there every time with a heavy kicking rifle like the 375 H&H. Winchester learned this late in the game and started doing this with the 458 Winchester stocks late in production. My smith says Winchester should have done this with the 375's too, "it would have saved a lot of good stocks"....I've been looking for a good 375 stock for gunner, and this is what my smith had. Some would sneer at the price tag, but it's pretty much original, with the exception of the modification. Which by all rights makes it a better stock. However, in the eyes of a true collector, the price needs to be lower than a 100% original specimen. Here's that stock. I will also show you a pic of the price tag and I'll bet my smith will get that much out of it:
Here's my 375 in this stock. It fits great, but still needs to be glass bed. That will also lower the value of most rifles, but most of us know that a good 375 H&H needs to be glass bed in its stock or it's going to crack if you shoot it too much. It's inevitable...: