X-heads vs J-heads: what's the difference??

str12-340 said
J-heads first appeared on the 1970 1/2 340 six pack motors, but had relocated push rod holes that moved the pushrod away from the intake ports allowing most of the vertical hump just inside the intake port to be removed for much better flow. These "TA" heads all had 2.02 valves and special adjustable rockers that don't fit any other factory 340s or 360s. None of the other J heads did this, but the castings are identical - it's all in the machining of the pushrod holes.

The small block has that screwy pushrod geometry as a result of Ma Mopar retaining the cam position and lifter valley angle from the poly-headed A engine. I like what Ma Mopar attempted to do with the TA head - offset rockers to move the pushrod away from the port and eliminate the "hump". That should have been standard on all the heads.