as I said earlier, over head cam is better again. 7500 rpm on those dates were unreal numbers especially if you had a pushrod. 60 and 70's were dominated by US cars and engines but since then they haven't updated till late 90's, because Camry or Accord are most sold cars in US they realised that its time to wake up. Thats the reason they are coming out with better engines. more gas milage and more power.