mate if you want the best of both world, in my opinion your better of with the A14 it will rev but will also be a lot torqueir than the A12. the A15 has bags of torque but in my expirience doesn't like reving past 5ooorpm. they start to shake heaps. now with the A13 that one of the other fellows mentioned, from what i found out is that the A13 is an A12 block with an A14 crank and rods with A12 pistons.