100hp per litre can be hard/easy to obtain most of this will depend on the head got any pics of ports and combustion chambers? the best way to achieve your goal is to get the head cleaned up, bigger valves would be nice if possible, Itbs on a nice matched manifold, good headers, most compression you can go on 98 and then cam it to suit (all the na basics). If your motor flows well you will need less cam to get the desired hp figure and have a more useable engine ie. wont have to rev the tits off it