GMC Siera GT ?

[Sixball]

I bought one about 11 years ago. It was a 94 1/2 ton shortbed stepside. It had about 230,000 miles on it, but it was solid, no rust. I used it as my daily up until last year. I could tell the 350 was on it's last leg at about 340,000. So I decided to make it my project truck and threw in a 454. This winter I'm doing the body and suspension.

My question is: What makes it a GT? The interior seems the same. It has painted bumpers, but aside from that, were there any engine / rearend mods? When pulling the 350 out, it seemed like it had an extra trans cooler. But I didn't know if that could just be a towing package? Or specific to the GT ? I kept it sitting the last few years only using it when I needed a truck. Aside from needed cab corners, the body is still solid and straigh.

Any GT owners out there?