Whats a "U" head?

340butterduster said
That is an LA head, '915 casting, some had "X" some had "O" some are "J" also some "U" (i believe). with 2.02" valves. Used on 340's and 360's.

Hope this helps.

really? I learned something new, I always thought that J and X were the only two heads on the 340 and 360s