8" High boxes?
I got mine out of an Acura Integra, They were mint condition and I think I paid 50 bucks for the pair. If it would help you I could describe what I did with mine.
But by the sounds of it you may not have Rails to go with yours.
I added 11.5" 3/4" Plywood the same width of my seat on an angle forward and backward. these were anchored to the floor with L brackets and the rails were bolted with Large fender washers to these wooden pieces.
I wish you lots of luck, but keep it simple, you shouldn't need anything fancy, just something that will allow you to pin the seat when it is in the flying position and be able to unpin and slide out when your done.
Trev