I used a combination of the original fold/tumble bench seat holes and a few new ones. For the rear part of the seat you'll need to cut down the mounting plate to get it to fit. At the time I was running matching LR3 seats in the front as well. After my rebuild I decided to go back to the stock Defender seat set up.
RIP 1994 D90 #999 (engine fire 2002). We'll miss you.