Seeing your post I had a quesstion and thought
1. Never hear that story and really don't understand the logic but dod the casting dates on your heads "go" ith the rest of the engine
2. Ford's documents of the time don't mention such a change. The Technical Service Bullitens of the time would be the place things like this would have been share with the service department. Such a change would be a major item to mention considering that they even included very little detail changes in production. Examples in 68 included change in spark plug heat range, crank shaft pulley bolt change and so on
3.Another thought would be why would care if late 390;s didn't breath well? In fact this would be a great way to sel the CJ's in place of the 390's
Sorry but we hear tons of stories and few if ever pan out.
Do always love hearing these though. Best one so far IMHO was the one where the 65 Shelbys were built with 6 cylinders (guy even claimed he had one of these rare engines

And Shelby swapped the K engines into the car while at his factory
Car looks great... always loved the 68 fastback GT's
Jeff Speegle
MCA Shelby Gold Card
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Mustang & Shelby research, documentation
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