I don't know if my 46 is much wider than your 40, but I don't think so. I used seats out of a 98 mark VIII, the out side holes match right up to the 46 seats so I just had to drill the inside holes
by the hump. You will have to build a riser as the mark seat slope
to the front some or sit level.

If you have a 2dr the back seat will fit right in, just lift the back off of the holder, take out the bottom, put the bottom in place from the Mark. You might have to bring the front of the seat up some, take a 2x4 and screw it to the board that is there. I let the 2x4 rest on the tunnel hump and just leveled it from that. Then just hang the mark seat right on to the holders for the 40 back they fit right on, change nothing. When I got mine I got all the seat belts, the bolts, all the hardware for the belts and put them in also. Front and back.

The seats are electric every way, plus heated.