I have a 2000 ls400, very low and I’m putting in a new rear subframe to raise the differential to go lower. After disconnecting everything from the rear end, the only wall I hit is that the front differential/ subframe bolts are loose but won’t come out (they are not free spinning)

I circled the bolt giving me a problem

 

By free spinning you mean the captive nut? That is not spinning in the frame? What happens if you try and tighten the bolts.

 

Captive nut? What do you mean? If I try to tighten or loosen the bolt it gets too tight to move.

 

The bolt threads into something, often that will a nut inside a boxed piece of steel or welded to the frame. Captive means the nut is not designed to be removed.
Oh a seized bolt. Classic problem hit it with penetrating oil many times over the course of hours or even days. If that fails heat the bolt.

 

It might be captive, I’m gonna just cut it off and replace the bolt