For years everyone had to modify the sheet metal and body to work around the shape of the glass. There is a company now offering custom glass at a much more affordable price. I am doing an Impala that has a funky rear glass that I want to flush mount this is why I was looking for alternatives.
I met the company at Nashville Goodguys and their card is in my file which is not available to me at this moment. I do however know that they are the company that did the rear window on the Buick done by Rad Rides by Troy.
Just found it. Here is the link:
http://amhotrodglass.com/am/?p=410
Good luck