Proper I.D. for T/A head?
j and u are the same head...i think mine actually have a U on them...
found this at
www.allpar.com
Some of the 1970 340 Six-Pack engines had heads with a U or O casting letter in addition to the J, but they were still the same part number head (the T/A head had the intake valve pushrod holes drilled in a offset location).