There's no special collector's value attributed to it (over/above most other M37's in like condition), so use it as you wish, or alter it if you want, since the value wouldn't change very much no matter
Not true. If you follow the price of old Ithaca 37's, you will see that they are appreciating in value pretty quickly. Locally here, a beater 16 goes for almost 300.00. There is a not bad 16 for 550.00 local.
The older they are, and in good shape, the more they are appreciating in price. Add in that a new one goes for 800.00 plus, then the old ones start looking pretty attractive, especially for a gun that was largely hand fitted.
If he chops the barrel, or otherwise alters it, it quickly falls down into the realm of a parts gun, as it will no longer have any value to folks that collect Ithacas.
there are a couple forums especially dedicated to Ithaca owners/fanciers
you can join these and get some more information about your gun. there is lots of knowledgeable folks/collectors on these sites