you can't really do that much with them mechanically i.e. camshafts, porting etc. because the head and the block start fighting each other (in tuning terms) summarised, this means that anything you do to the head will make it want to spin-up faster, but the long-stroke nature of the block will fight against it so anything you do will become self-defeating and produce only very small power gains. If you were determined enough with the block, lighter pistons, race-spec con-rods and a lighter flywheel would be the way to go before tuning the head to suit, but again i wouldn't expect much out of it in terms of mid-range torque, it'll more than likely end up with top-end power and nothing else below and still not much improvement over standard.