Here's what Wikipedia has:
The 4JG2 is a 3.1 L (3,059 cc), 95.4 mm bore x 107 mm stroke version with indirect injection. It replaced the 4JB1-T in the Isuzu Bighorn (Trooper II) and Mu/Wizard (Rodeo) in most markets. This engine was upgraded from mechanical injection to electronically controlled mechanical injection.
The best Isuzu engine is the bulletproof 2.8 Liter 4JB1-T, a great choice for a Defender style Land Rover.
The later 4 cylinders came in 3.0 & 3.1 and were known for problematic.
All the engines in the 4J range would eat up a series transmission.
The OM617 or the Diahatsu 2.8 TD are better choices.
Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)