The GS is a Beaut...
I have a 74 GS, with the Buick 350. Only 400 were done in 74 with the 455, tried to find one but Got what I could find. Only 51,000 miles on it. It's my favorite as it has never let me down. I drive it all over.
I didn't know Hagerty doesn't write in Mass. Grundy is good from what I hear. Similar I guess.
The GTX is an interesting car, when we got it no one knew it was matching. I was told it might have had a replacement block. We found and verified the numbers. I loved it as it is un-molested. And basic except for the Automatic. Just pure muscle. My wife re-detailed the engine compartment with engine in place. She's good at that.
Keep that GS humming.
and Maybe we will connect.
numbers on my website.