Sony is the only studio I've seen follow aspect ratios on cartoons to the letter, as seen on the Magoo and UPA sets they released. Warner didn't seem to be that concerned about consistency as the few cartoons I've been able to examine don't match up. Heaven Scent, released in 1956, looks like it...
All Warner Archive Blu-rays are pressed and all animation releases have been uncut, other than irreversible changes made for reissue where original prints aren't in existence. I was pleasantly surprised to find the 80th anniversary Bugs set had more than a few cartoons with original "rings"...
I'm pretty sure that the only Looney Tunes releases I ever purchased in-store were some of the Super Stars discs. All the Blu-rays were from Amazon, as were all the Golden Collection sets. Those were all pre-orders for me back in the day. Though, I do recall picking up most of the Walt Disney...