never seen a raised "J" on any 4323302 cylinder heads. but I'll take Rug_Trucker's word on that one.
the #1 reason why nobodies to fond of them is hardly anybodys ever done serious work on them.
Ryan @ ShadyDell(?) has done a few sets, IMO the flow #'s where fantastic, with alot more left in them.
If you can work past the pushrod hump (like I did), they flow baby! There's an old nickname for the "302s"... the W1.
As far as the 0ld 273/318 heads, they make great anchors. they are really thin along the floor and roof,
and theres not much you can do.