There are two 270 small port heads. The early domed chamber was used on all GMCs 228-270. There is a later 270 head with a D chamber more like the 302 D chamber head. Mine is the later head I think the valves are stock size but it is shaved .035" and the ports cleaned ups bit. I would go with bigger valves like 1.86 and 160. Small ports work well on the street and is what Bill Fisher recommended for the street.
