The center point gets changed and shifted over alittle.You have to remove the outer seat locks(for the backrests).
You can see in the pic that the jdm backrests bolt to the floor(there are dimples in the area).You have to drill and install theaded inserts to bolt in the seat.

I hope this helps.I have more pics but they are on my crashed comp. . I'll try to take some new and better pics tomorrow .