340 X heads

toolmanmike said
My Galen book says 68-71 were X (2.02/1.60)
70-71 360 were J,Z, or O (1.88/1.60)
70 TA were U or O (2.02/1.60)
72 340-360 were J (1.88/1.60) I would imagine the 73 and 74 were J's as well although they were listed as a different casting number. (3671587)

I saw the question asked many years ago but don't recall the answer - "What did the different letters mean and were they casting # specific?" I don't normally use the letters as a reference, just the casting #'s because it gets confusing. Anybody have any additional info?

'68-'70 340 = 894
'70-'71 (-'72) 360 = 915
'70 T/A = 915
('71-) '72 340 = 915
'73-'74 340 & 360 = 587

As far as I know, only the 894 X head had "340" cast into it while the rest had "360".

I borrowed these pics from another members post a long time ago. I believe the story was that these original bare X 894 castings were machined with T/A intake pushrod locations by Mopar during development before 915's were available. Only 915's were eventually used on T/A & AAR production cars.