Hey guys ... the OP is after an A series

This means the only options are:
2.3, 2.5, and 2.8
2.3
Old old school. She is an old engine and lacking in the horses. Fitted to the Carlton and resurrected by GM for the LWB A series only. While you will never get speeding ticket they are great off road and will pull anything. I have had two of them so far and to be honest they are a simple chain driven engine that will just plod along.
2.5
Italian VM engine. She has power and when running does a good job. However that comes at a price .. literally. Very temperamental. Often plagued by lots of niggly issues that can cause it to go into limp mode. Parts aren't as readily available as the other two. Also the only one of the three to have an ECU
2.8
Isuzu at its finest. The best of the bunch in my opinion. Simple, powerful, and reliable. I have this engine in my Trooper. Its an old design but with TLC can last you years and still keep up with more modern engines. As an example I am running with 31" tyres and combined 6" of lift. My old Trooper is breeze block aerodynamics and I still return 38mpg on a run. Con's are that they are the desirable engine so finding a good one as cheap as the others is difficult, and they only did a limited number of them before moving to the 2.5.