well, the next step is check all the differing details between 64 and 66 - must be a number of changes in 3 years that could give a hint - like maybe in Gunnell's book on old Chevy trucks
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics