60/55w H4 bulbs are EXACTLY a power match for the 60/55w halogen capsule inside the sealed beam stock headlight. I would NOT go any larger. In fact I remember that when I installed my relays and direct battery power feeds, even the original headlights were brighter. After my upgrade to 100/80w bulbs, I was a happy camper. But I would not run high power bbulbs on stock wiring.