The Forgotten On

I would get a bit destructive and break the bolt heads off with a chisel and a hammer, but that's me.

Wisconsin Joe

Can they even be reached that way with the seat all the way back?

I think the seat rails (movable part that the seat itself is on) ride back over the bolts.

I think they are completely covered.

I would soak the jack screws in penetrating oil of some sort.

If that doesn't loosen them up, then you may have to cut the seat frame to get it out.

It may take a fair amount of force to get them loose.
When I got mine, the seat switch would work going back, but not forward.
So every time someone tried to adjust it, they ran it back (it was already all the way against the stops) and tightened it up a little bit more.
The fact that the jack screws were just a bit out of synch didn't help either. One was not quite against the stop, so the other was really tight.

jpitman2

When I had to pull my seats to get them recovered, I found access to the rear bolts relatively easy once I adjusted the seat height to the top of its adjustment. As practice, try removing a seat from a Miata - I have done 2 now, to fit roll bars, and both needed extenders on the socket bars to crack them.
jp 83 Euro S AT 57k