It would have to be different construction for all the balls.
John McCain would be just the guy to check this out...but not within 90 days of any actual baseball game.
McCain/Feingold CBR 2007 - Core Baseball Reform of 2007
LOL! But would players be allowed to spend their own money on balls?
The bottom line is that if there were a bunch of "juiced" balls being used, there would have been a lot of players with 40 and 50 plus home runs not just McGwire and Sosa.
I suppose if they want to prove it, they could put ads out offering $1000 or something for fouls hit by McGwire and Sosa. For this story to have credibility, they need to find at least one baseball that was used in a game that is cut open and shows these irregularities. My guess would be that several hundred thousand baseballs are used every season, it shouldn't be that hard to find ONE if the story is as widespread as they claim.