351 heads ?'s

I've even heard of the J code referred to as a high performance 302. The G code is the only real high performance 302 that I know of.

The 68 J code was a higher performance than the 2 bbl engine, the parts that did it were the heads (increased comp ratio) and the 4 bbl intake and carb. Not sure if the cam was different though. Really the only thing different about it vs the 83-84 HO 5.0 would have been the comp ratio, the cam grind & the ignition.