witch are the best flowing 273 heads#

"302" castings have the same (1.74"/1.50") size valves as typical 273/318 heads. They have a more modern exhaust port and chamber shape. They were the best of the pre-magnum LA small port heads. They also respond well to larger valves and mild porting. A bore notch is typically used when fitting 2.02" intake valves to a 273, but it's probably not worth the hassle for the small gains over 1.88" valves. You could fit larger valves and port 273 heads and get similar results, although I don't know why anyone would bother unless they wished to retain the oddball 64-65 intake bolt angle.