Have a 9n tractor with loose lower link where it attaches to tractor. Both sides have a bolt but it just turns like there is a nut on the inside. Any suggestions how to tighten this?

No, have you started losing fluid yet? The only remedy for this would be to drain the fluid, have it drilled and have a helicoil inserted and hope that it holds. This is a problem with the older fords in the 2n, 8n, and 9n. The only other option is to remove the rear end housings and go inside and place a nut on the inside of the unit and braze it in place, and this is a major job. You say the bolt is stripped, so it is time to make the repairs. I wish you the best of luck with this. As I too am fixing to have to do this to our 8n and am dreading it.

Have a 9n tractor with loose lower link where it attaches to tractor. Both sides have a bolt but it just turns like there is a nut on the inside. Any suggestions how to tighten this?
Just a quick update. I drained oil and pulled pto shaft and they did have nuts on the inside with cotter pins and had just worked loose. It was a very tight fit to get my arm in there to pull the pins and tighten the nuts but I finally got it.

Good job, I am glad you got it.