Stevens 5100 SxS

DO what pleases you and let the Buddy do his thang! I doubt the turkey or pheasant will care which barrel the kill comes from in the end.

1939 isn't that old for a side by side. Not sure where you're located, but if you're limited to 2+1 loaded rounds, the double isn't much of a disadvantage. You may not get the super extra full turkey choke, but I'm betting a lot of birds were killed over the years with plain old 2-3/4" shells in plain old shotguns.

It might not hurt to have a gunsmith check it out; but I bet he'll give it a clean bill of health. The 5100 is a classic American SxS,
Don't forget to pattern it for turkey hunting. It can't hurt to know how it shoots when after pheasant, either.

I can't see why it wouldn't be fine, they're great guns. Maybe if you put a tactical pistol grip stock on it your friend will approve.

Two warnings though: If its got the Tennite (plastic) stock, take care as they're supposed to be fragile at this point, second, steel shot would definitely be a no no.

Mine is a 1947 vintage, it shoots like it’s brand new.
I’ve taken quite a few ducks and 1 turkey(using #4 shot).
It’s hard to beat a 16.