hello mate
some 4x4 had a red top, basically only real difference is the green top had a cat and all the accoiated engine manegment i.e. lambda sensor in the exhaust, different ecu.
the 2wd and 4x4 are totally different
block, sump, head,pistons,inlet and exhaust manifolds, and the list goes on, but most thing are interchangeable as far as i am aware(with some modifications),
hope this helps
RegardS nick