Well wifey's never gonna stop kneeing me while I sleep, but the heep (1990YJ) ride will now be much more comfortable for rear seat passengers!
My 1990 YJ's rear seat is 5" further back than it was earlier today.
Fist I removed the seat, then all 4 mounting brackets.
I measured the front bracket's hole pattern & found them to be 5" between the two holes of each side.
Next I bolted the front hole of each bracket, to the rear hole in the tub.
Then I carefully looked under the tub, to see where these new holes would come through.
The drivers side was not a problem, but the passenger side was above the muffler heat shield.
Since my Thrush turbo can, is nowhere near that, I went ahead & drilled through the tub & shield.
Triple check your job, before drilling!
Never drill through anything, without knowing beyond a doubt what's on the other side. If you are ever drilling & suddenly smell gasoline, stop drilling at once!
Using a longer bolt, I drew the shield up to the tub. (About 3/4")
Then replaced that bolt with one that was midway between the first bolt's length, & the stock bolt's length.
The side brackets were really easy, since my plastic fender liners have been in the shed for 8-9 months now.
I measured 5" back for each hole & made a mark, Then measured from the bed to each hole & transferred them back.
Nylock nuts & fender washers on all new bolt holes!
The space behind the seat has shrank a little, but it's well worth it to me!!!