The rear wheel arch seating mount is just spot welded onto the wheel arch, drill out the spot welds ,and presto its off
Depending on your road laws, changing seating capacity from whats stated on the VIN plate entails a mod plate over here,check your laws before doin it
The seat with no brackets is a 2 seater style seat, the seat with brackets should be a 3 seater type seat,unless you really,really have to swap the seats dont bother
Fuel filler pipe, inside the fuel door is a few bolts, undo them ,that attaches the fuel pipe to the body,pull it away from the body somehow to remove body, failling that, undo the fuel pipe/pipes from the tank , then when new body is fitted reattach,dont forget if doin it this way, you stuff a rag or something in the tank to stop stuff falling in
The bolts your having issues with,throw a pic up .....