if you peeked back there you would see that the nuts are what you remove to get the seat out. This means that the bolt is really a stud that is welded to the floor. So just getting longer bolts is not an option. The lifted bracket will have to be secured to the floor with the original nuts (on the exsisting studs) and then the seat will have to be bolted to the lift bracket with new botls.
I just pulled my reat seat out today and plan on doin the same thing.