I believe the fins are all the same. @CudaChick1968 can chime in. The spark plug wire insulators are the same for 65 and 66 and of course the 67's are double wire holders.
There are only three differences in fins as far as I know.
One style have full rear upright posts where the rubber grooved spark plug wire retainers slip in and fit. The other style has a small slot in that upright where the white plastic wire separator clips in. New plastic retainers are easy to install but difficult to remove without breaking them.
All were fully polished from the factory but only some stayed that way. Most have argent silver in the recesses between the fins.
I have noticed another difference too in the larger side wire harness retainer. Some are 4" wide and the others are 3 1/2".
Thanks for the mention @toolmanmike! I have a set here in line right now for a new Hawaiian customer.
