Trying to get the profile of the rear flare to match up to the GT rockers. It seems like I had to take a lot of material off the bottom of the flare to get it in where I wanted. Are there any standards that say how far in/out the flare should be as compared to the stock fenders?

Take a look at the pics below. The front portion of the flare has been trimmed to bring it closer to the body, while the rear has been trimmed so the rough edge (where it gets welded to the body) sits flush. Should the front and rear be flared away from the body equally?

Front of rear flare:


Rear of rear flare:

Nothing is going to sit flush until you get the old lower section cut out. After that the flares won't sit PERFECT no matter how hard you try. You will have to use many vise grips to hold it in place and hammer and dolly both the flare, and the body to one another. Do not concern yourself with the pics you posted. None of that metal will remain, so there is not any point in even looking at it when fitting the flares.

I'm overthinking this way too much. Cut them out and weld them in!

It's that measure fifteen times and cut once mentality I've got.

From where you have it clamped, scribe a line, remove the flare, and cut on the inside of the scribed line. Replace the fender and you will see it fits closer to the body, it is a gradual process to get a "perfect" fit, and as I said, even after doing this 3-4 times you still won't get a perfectly flush edge.

That's right, just do it!

Click to view attachment

Looks Good!

I am glad I read this !! I had the same questions.