I am unsure exactally how similar the BH chassis is to the BJ although I know a BP-T bolts straight into the1500 BHs so if thats any help to you at all...

Wana see the wonders a Toyota supra box does for a mazda GTR running 320wkw? From a Mazda box which fails with much less then 200wkw you get this!

http://www.youtube.com/watch?v=FfgAjbKjP1c&NR=1