As per my limited knowledge of the subject... rocky differentials come in three ratio's
37/10
37/7
37/11
my jeep has 37/10... and its good on-road and an okay offroad performer.
it is very important to choose proper ratio's of gear and differentials.... according to the engine RPM... some engines like 2L are low rev... others like 3C are high rev... take these issues in account.
my setup is 3CT engine... with rocky 5 sp gear and 37/10 differentials... and i love driving it 
abt ur engine of choise... look for its performance rpm, gear ratios and match a differential accordingly.
i suggest dont use rocky diff if ur using prado gear.. go for matching prado diff... will cost a bit high..
and rocky gear is known to b a little noisy 