Valve length really depends on what you have in mind for the heads. If you are doing a stock rebuild, then stock or near stock springs will be used. There is .090" difference between those two valves - or a nice .060" locator under the valve and a .030" shim for the taller valve to have the same installed height as the shorter valve. So either would work. Another consideration is whether the valves are recessed into their seats, because that might require the addition of thicker shims to maintain the correct installed height for the springs. After the valve job is complete, test fit the valves and see which one is closest to the correct installed height required for the springs used. What worked best when the head was new, might not be the best choice today.
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Mick Batson
1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 Catalina Safari Wagon.
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