I dont want to change out the pistions or crank, but what is the biggest cam i can put in? I have a 1968 289, or 302 not sure, but it is a 'c8'so i have heard good things about this block, and also has the made in mexico on it with a stamped '302' on it.i have ported the heads (which have '289' on them). Now if I want to put bigger valves in my heads, say 2.02 and 1.60, what is the biggest cam? thanks