I looked on Thingiverse, and the two GT models on there are pretty low Poly count. I am looking for one that I can customize and 3D print around 11" in length. I need to customize for my front bumper, and my custom side scoops.
I have a cad model, but its pretty low resolution likely similar to what you found. Here are some screen shots.
On a side note... I have access to a laser scanner that produces an EXTREMELY high definition model. I have wanted to generate a laser scanned model of my 86GT, just have not had time yet. Someday. This would generate a 100% accurate electronic model that could be used for measurements, detailing or printing. This was quite similar to how the new GT taillights that are being produced were able to be such a perfect replica. Could even be scaled down and someone could 3d print a 1:18 fast back for all of us who want one so bad.