I found the front two. But where is the back two? Do I need a special swivel to get at it?

 

pull the seat all the way forward, one is under a carpet flap, the other is supposed to be under a plastic cap you pull off.

 

Seats don't move. :/ rusted. Oh well time to pull out the wd 40

 

You may be able to get at them with a swivel socket(14mm head on the bolts) ,but honestly you gotta be a Gymnast to do it!
Stuck sliders are a total snot bag!
I had a set that I bent the seat up enough and cut the damn things off.I had Zero Patience that day!
If they were not stuck,slide seat up,boom,.accessable.