You can try your local car glass replacement place. I did get one a few years back for the hardtop locally. FYI, when you talk to the local car glass guy make sure you specify hardtop. The post cars take a slightly different windscreen and they are just different enough where they cannot interchange. Way to go Ford.
I have a '63 1/2 and one of the tech manuals that's available for it is a 1960 - 1964 Ford Car Master Parts and Accessories in two parts. The first book is an illustrated parts breakdown (IPB) and basic part numbers for all the Ford cars being made for those model years
(full size [Galaxies], Falcons, Thunderbirds, Fairlanes). The second book is text which gives you the complete part numbers and other useful information. I have attached an example from both manuals having to do with Galaxie windshields. You will see from the IPB that the basic windshield glass part number is "03100" and that part number is used for more than one car model. (That might even possibly be the basic part number for the windshield glass in your '66.) To get the full part number for the right part for your specific model from the "Text" model, a prefix and a suffix are added to the basic part number. You will also notice that Ford has thoughtfully provided a "NAGS number". This stands for National Automobile Glass System and is the part number your glass dealer should be using to make sure you get the correct part. When I had the windshield replaced in my 63 1/2, I provided my glass dealer with the NAGS number, for which he said he was thankful, and got a good job at a reasonable price. I don't know if your '66 model is included in an available Master Parts and Accessories book. One would think it should be. I hope I haven't wasted your time with all this. Hope you are successful however you do it.
My 66 2DR HT front windshield had poor visibility and the rear windshield leaked. A couple years ago I had a local guy replace the front and reseal the rear (Jacobs Auto Glass Spokane's PremierAuto Glass Specialists!). I can't find the receipt, but it was in the $400-450 range out the door. I was surprised when I called him and after some keystrokes on his end he said "Yeah, bring it in". I did 2 days later. I thought it would be a big deal to find the glass and order it, perhaps at a premium. I'm near Spokane, Washington.
When I got the car, rear glass leaked and front glass was cracked. My local glass company had a guy come over and pull the glass, I did some rust repair and a month later he came with a new windshield and put front and glass back in - cost me 450 including the new windshield.
Its like pulling teeth to give some one money to do anything anymore.
Found 2 shops, both people on phone told me nope cant get it. Both shops Techs called me back said they overheard conversation.
One wanted 525. Other one 380.
Glass is in NC so should in, in a couple days
Went through same thing with painting the car. Got tired of trying to force someone to take money for work, painted it myself, could have installed glass too, but sheesh, trying to support local businesses.
I will let you know, I am running the numbers on a new shop with spray booth, and we will probably end up doing glass too😃