547 Buick GNX'S were made in '87. All were virtually identical in trim and driveline. All were single turbos. They were rated at about 275 horse, I believe.
GTX was a Plymouth from the Belvedere line. They came out in '67 under the name & emblem "GTX". It was basically a fancy Road Runner with better & more attractrive trim, except the Road Runner was available with the 383 as standard motor, with the Hemi as as the only other motor option.
They came standard with the 440 CI, and the infamous Hemi as an option. The standard 440 was rated at 365 horse with 1 carb, and 375 horse with a different carb. In '70 they were available with the 6 pak, 3X2 Holley set-up, rated at 390 horse.
Do not be dising the GNX on this site, or any other. They were exceptionally fast and quick for their day, very limited (547 documented), intimidating due to the all black color & red GNX badging, and to this day maintain a following that is just somewhere short of "Cult" class. They are pretty much the first and last class acts of Buick, and are considered quite collectible on today's market.
For further info:
www.turbobuick.com
wwwturbobuicks.com
www.gnxforum.com
www.gnx.com
www.ihadav8.com
www.t6p.com
www.hightechhorsepower.com
Thanks for your consideration