If you look in the wiki Dodgeman with the help of DDgonzales got some a12a rods which have larger pins to suit the larger pin A15 pistons. Instead of opening up the early rods (that is if you have an earlier engine you are building) to suit.
At this stage you save money on cheap rods and make up with a lighter flywheel, A14 pulley (lighter than A12), maybe a little lightening the crank and the rest your call for a revvy high torque hybrid.