[Guest]

I've got a 67 coupe with a code A 289 per the door plate. When replacing spark plugs I found out that the standard 18mm BF 42 plugs are too big. The previous owner has autolite #26 installed. These are 14mm plugs. So now I wonder what engine/head is installed.

 

[65fastback6]

Sounds like you have a newer 302 engine or heads.
If you could get the casting numbers then you could
get an idea of about what year it is. The number
would be like C7AE-6010-E. C7 = 67, D7 = 77, E7 = 97.