This information will likely be useful/interesting to about 3-4 people out of the whole group here but I thought I'd post it anyway because I know there's 2 66 Grande Parisiennes owned by two different Kevins who will want to see it! One of the Kevins owns my old 427/4 speed 66 Grande Parisienne.

40 years ago I had my 427/4 speed Grande Parisienne. One of a few rare options that car had was an original power antenna which mounts on the passenger rear 1/4. These were unique to Canadian Pontiacs. The US models used a completely different power antenna, mounted in a similar location but it sloped back at quite an angle vs the Canadian antenna that is vertical. Also, the bezel and nut on the 2 models was completely different. One night I foolishly left my car parked on the street in Winnipeg and of course some idiot broke the antenna off. Even in the 80's it was impossible to find an original (or so I thought) so I replaced it with a universal aftermarket unit. 

Fast forward 40 years and I want to put a power antenna on the Grande Parisienne I own now. I start researching, reading as much as I can on them (which is very little as they are almost impossible to find) but with the help of a good friend who is into 66 full size Chevys, I have a lucky strike. I showed him the assembly manual drawings for the Pontiac and he says "that looks a lot like a 66 Caprice antenna other than the bezel at the base". I do a lot of part number comparisons and he's right, they are mostly the same components. Then another lucky strike, he says "the Caprice antenna is almost identical to the 66 Corvette power antenna". Of course when it's a Corvette part, the availability gets a lot better. 

I purchased a 66 Corvette power antenna in nice shape and the hunt was on for the totally unique bezel. As expected, impossible to find. Next option, modify a bezel that is close but doesn't quite have the right angles, make it the correct angles.  After much digging around , and with help from Beaumontguru I narrowed it down to maybe a 72'ish 1/2 ton bezel. Close, but not quite right yet. However, Beaumontguru and I were slated for a trip to my (likely our) favourite wrecking yard for old car parts, the yard I talk about in Minnesota. He pointed out the broken remains of a rear manual antenna located on a 64 impala 4 door hardtop. They used bezel similar to what I needed so I purchased it. I measured the angles on my yellow car and did a mockup with an piece of quarter panel coincidentally from a 66 Pontiac. I kept working with filing the base of the bezel until the angle was correct to mount the antenna vertically. This is how that looked. 

And this is how it looks mounted. Only an absolute 66 Canadian Pontiac fanatic will ever know this is not the original bezel. 

The only thing I have left to do is make a mounting bracket from the motor to the inner quarter panel brace, as shown in the assembly manual drawing.