I have some afr 185 that where made in 2005, part # 1387. I need to do a valve job so i had my machine shop measure them for me. I cant find any valves to fit it. I called AFR and they say the head is told old and they dont stock valves for it any more. The stem size is 11/32 but the length is whats getting me. They are 4 and 15/16 long and i can find any valves this size on summit. Can i use a different length valve that is a more popular size?