All small blocks share same crank ?

Just because the tires are new and balanced doesn't mean they are not the problem. I just worked on my friends Lexus, he said it has a thump from the rear at 80 mph. I removed the rear wheels, 1 wheel was bent, and 1 tire was bad. He just had 4 new tires installed. Both rear tires were at least 4 oz. out of balance each.
We had 4 new tires mounted and balanced at home and drive to Utah, we experienced a vibe at 80 but it went away down at 75 (?) so when we got to St. George, we took it to the same chain and had them look at it. Both rears were out of balance and one had a broken belt (big dimple on side of new tire side wall.."uh, is this supposed to look like this?" ...Nope. Did we toss a weight too? Doubtful, as the weights were stick on's inside the rim and there was no where for them to go. So we got a new tire and a balance job under warranty. They were very nice about it too. Butter smooth on way home until we hit the crappy CA freeways, then it was just loud. We pay the most in fuel taxes but have the shittiest freeways? Oh yeah, I forgot who's running the show here for the last 30 years.....