The exhaust is a pretty simple thing to make under a Pajero. It's basicly a very easy downpipe, a straight pipe and a kink over the rear axle that has a little angle to the right to get it hanging under the framerail and away from the coil.
This is done to almost every beefed up diesel truck in my neck of the woods and compared to a pickup toy or a GQ Patrol this is quick and easy and as a result cheap. I found some extra horses when I did this and they only wake up when I go uphill in high gears. Hills that demanded me to shift from 5th to 4th suddenly were doable in 5th.
Puting a 3" on an engine this size is probably more of a personal choice than perfomance gain over the 2.5" and also the 3" can not be bent over the rear axle without a kink unless it's mandrel bent.

2.5" and a single resonator with a down facing end tip, can't go wrong with it and your'e set for future turbo mod's. <img src="/forums/images/graemlins/kewl.gif" alt="" />