Better to reshaft or extend vintage irons?

What does extending do to the feel? Will it change the way rocket shafts feel?

Not significantly IMO. I’ve done it and it works fine. Adds a little weight to the back of the club, but nothing crazy. Extending also increases the swing weight, of course.

Reshafting really old irons is a serious chore, nothing like reshafting modern clubs. Only do it if you need to.