Here's the problem, the engine don't fit. Here are three pictures that show the difference in the left and right engine frame mounts in question. The car is a late March 66 Fastback and the mounts came a box from a want-a-be restorer (who shall remain nameless for now) back to the owner. I think the one on the right (in all three pictures) is a genuine 66 mount, the one on the left is a 67 only mount.
Pic 1 - Note the frame mount bolt hole's different location.
Pic 2 - Different tabs on the engine insulator portion. Note the faint letter "R". The other bracket has no letter ID.
Pic 3 - Different mounting brackets, the angled cut vs the rectangular version.
What I want to verify is that the bracket on the left is in fact a 67, or possibly for a 68 on convertible.
The car's owner, sitting here drinking a beer and eating walnuts, asks, "Does anyone have pictures of a pair of 66 engine mount, a pair of 67 engine mounts and a pair of 68 thru 70 engine mounts to do a comparison." I know that the 68-70 mounts will fit a 66 and 67 is the odd variation. To keep this simple, disregard convertibles.
Jim
