i got the basemounts for the mkiv supra and fitment is horrible. if you already have basemounts (from the 240), i'd look into getting a shop to modify these to fit properly (if this is possible, i don't know anything about 240's). No point in spending 200+ for supra brackets that don't fit either.
Don't get me wrong, i got mine to fit, but don't ask how, and yes my seats are crooked, the base is stretched, so they don't slide for sh*t either, so i'm going to have to get them reworked in the future as well. (just don't have the willpower to do it right now, given the frustration to finally get the seats in the car).
(the seats also sit higher with the basemounts as opposed to stock, something you could also avoid with a custom base. There have been threads about this before, with many people also complaining about the terrible fitment of the basemounts, just so you know)
Luke.