Looking for 1100 magnum receiver only. Or close??!!

I am looking for a magnum Remington 1100 receiver. Trying to put together something for my son (9). His grandfather gave him a barrel out of the safe and he wants to make a gun out of it. I have a set of 1187 stock/forearms I think will fit. Thanks for any help. MC.

 

Why specifically a magnum receiver? There is nothing different or special about the receiver itself other than the rollmark on it.

 

It was a 3” barrel. I assumed the magnum receiver would be more capable of eating 3” spent
Shells. Just want to make sure a 23/4 face is not smaller and would not jam during extraction. But open to anything that will work.