It's been done more than once.
So it's possible.
Worth the trouble? That is up for debate, but if it's done right, you will probably be happy when it's done.
Getting there is the trick.
Good luck
Dave
Others are right. Getting the Mustang you want usually involves several mustangs. Fix 'em, sell 'em, make a little money. Buy a new one, fix it, sell it, make a little more money. Repeat until you have what you want.
Depends. If you go into it knowing you are going to sell it, you can make a little money off of a car. Where people lose their pants is when they decide to go all out, get bored/tired/broke and then try to sell it and "get their money back." That doesn't happen. I could never get what I have back in my GT. However, have a friend that just picked up a hipo fastback to resell. Cleaned it up, tuned it up, got it running well and made about $2000 on it when he resold it. He plows that money back into his "car fund" and his reach is $2000 more.
Know the market. Buy low. Clean it up. Don't try to make a killing on one car.
You can do it. You have to know, going in, that you're going to sell.
If it was worth the effort (seeing the prices of fastbacks these days) I would have started it a long time ago. Unless you have a jig to get your dimensions square, none of the interior or exterior molding, for that matter anything, will line up properly.
There are more than a few ways to go about something like this, and honestly it's not really a new idea. Someone on this post said 'if you are asking how to do it, you probably don't know enough to succeed yet' and this is for the most part true. There are the exceptions where someone has the physical skills, but doesn't know enough about Mustangs in particular. We'll hope you're one of these =).
The last link will by far give you the most information. Those people over there are more than just extremely intelligent, they're also extremely experienced. Bossbill has forgotten more than I've learned in 31 years about metal fabrication lol.
Oh, and fyi...I'm converting a trashed coupe to a fastback...but I'm going a totally different route!
I saw do it. They all started as coupes anyways. I had now idea what I was doing ten years ago when I was 17 and cut of my drip rails. Now everybody is doing it.
Your better off starting with the back half of a fastback, try to find a fastback thats been severely hit in the front, something that someone's not willing to fix, that would need a complete front end
Since your rear is all ready all apart, all you would have to do is cut the floor pan/rocker area and the A pillars, mate the 2, weld, and your done. No one would even know it was a coupe.
If it has good quarters all you'll need a trunk lid. maybe even buy a smashed fastback and part out everything you don't need engine/trans/rearend/doors etc...
I think if you have the ability to do it it would be cheaper than buying a fastback assuming you can do it all yourself. It might even be less work considering you won't have to weld in new taillight panel, quarters, wheel houses, etc...
I'm doing it. Have to roof and interior pieces. Even the mounting tabs for the rear seat. I am going to use a rear seat delete anyway. I cut the roof myself, it was easy enough. Take the time looking the coupe over to see everything that needs cutting.
Fortunately for me, I wanted my car to be thoroughly customized anyhow...so finding a totally trashed coupe was sort of a stroke of luck. I was going to keep it 'coupe' but I've always loved the fastbacks more. That's when the idea I'm currently working on came about. Building the lightest possible Mustang I can build, and still keep it 'restomod stock' appearing. That means stock type subframes, floorpans, firewall, etc etc. So it didn't really matter what bodystyle I started with, because it just turns out that my favorite first generation bodystyle is the one they make in 'glass =).