Removing J-Nuts from top of fender without removing fender?

[NJBronk]

Is it possible to remove the J-Nuts from the top fender mount bolts without removing the rest of the fender bolts/removing the fender? I'll be installing the Duff hood struts and want to replace hardware but feel weird putting the new bolts in the old rusty J-nuts... I figured I'd try to do all the top bolts at least but it seems like there won't be enough wiggle room to get the J-nuts out?