Technical Shelby 260 Performance Parts

Maybe the early 289 heads? They later stepped up to 63cc chambers compared to the 55cc of the 260.
As you say port changes and valve size changes also with 289 heads.
Alot of different part no's for 289 heads would indicate differences.

 

Yes, 63cc open chamber head was developed for '68 302, went on the '68 289 engines. I had a '68 289 years ago that had a 302 block, 289 rotating assembly from the factory being a transition year. The pre-'67 conventional rocker 289 heads are the good ones.

Joe