Um, according to the specs available online, the Isuzu Trooper RS has a wheelbase of 91.7" and the VX shows 91.8, 17" longer would be the standard Trooper at 108.7. The wide/narrow stance won't effect the placement of the torsion bars and even with/without those, it would still be considered the same "chassis". The distance between bars is the same on the trooper, VX, Rodeo and haven't checked an Amigo but will assume it is the same too seeing as the front 10-bolt's will interchange between vehicles. The wheelbase info comes from a few different car websites including edmunds as well as wikipedia and people who have documented it online. When you pick it up grab a measuring tape for us.
http://en.wikipedia.org/wiki/Isuzu_Trooper