Here's another example, started life as a 1969 Targa. I paid $7K to have the roof professionally grafted on by a guy who does hot-rod roof chops here in the SF bay area. He did not modify the rear quarters, and we cut the A-pillar as high up as possible. Kept the original Targa doors and sourced all the windows and window trim, it bolted in with no issues. I kept all the Targa reinforcements, had to get creative with the rear quarter trim and parcel shelf.
I had done a lot of work on the Targa chassis stripping it to bare metal and fixing the rust when I first purchased it back in 1995, when the entire car cost less than a set of wheels does today. For me, it was a much less expensive way to get the car I really wanted to do a conversion than to sell the Targa and start over. The entire project took 5 years, the car now has a 3.4 Motronic engine, mag case 915 trans, Carrera front and rear suspension with 964 brakes and a bunch of Elephant Racing suspension components. It is a blast to drive.