Xausa:

It is your gun. MANY times we look at old guns and wonder about the modifications made, why, and what stories they can tell.

My opinion follows:

If you don't need it and if you need the money, sell it. If you need the value difference between what you could get for it undrilled and what you could get drilled, leave it alone and sell it. Remember, a gun that is modified isn't worth NOTHING. It is merely worth somewhat less than one unmodified.

If you want a useful tool, a gun with which to actually harvest game, do to it whatever you think will make it a more efficient game-getter. If you decide to sell it some day, you'll get its modified value AND have had the use of it all those years.

That is why nI do not hesitate to chop, drill, rasp or file any gun I own.

But then, I am not a collector, and I do not invest in guns.

BTW: that is a dandy shootin iron!