if your dead set on using this gun, you csan have the barrel sent off to a GOOD gun smith, and if there is enough meat on it, they can cut barrel back a little and tread it fo chokes will fit in it(screw in chokes)
you will loose any collectable value to the gun, but it is an option.

but then again the price to buy another newer shotgun might be cheaper
a decent used modern pump shotgun should be had for about $ 150.00 bucks or even less if you shop about?
and will be way more accurate than this full choke, that might toss slugs at random points of aim??
which can lead to a missed deer or worse a wounded one?