Don't go down the money pit too fast. It's one or two parts causing the problem. That shifter needs replacing no doubt. I gave away my last stock shifter 2 years ago on stangnet. You are honestly better off upgrading. Don't get confused with which gear is causing which problem. Most of the grinding issues are "old clutch" related. How old and abused is the clutch in the car? How old is the ctutch cable?
I think I took that metal and rubber piece off and ran the factory arm on the factory base without it for a bit trying to firm up the shifts. If I remember I put the handle on the driver side of the shifter post. I got some big washers to cover the big holes in the factory shifter arm. You have to stop the slop from the big holes so I found two nuts that were thin enough to sit in the two big holes and were a small enough diameter to be tight in the holes plus cleared the bolts going through.. I put the factory bolts back in I think. That was years ago so I might be wrong on some points. Looks like it'll work from your pics though. Free if you have the bolts and washers. Plus no spongy rubber in the shifter.