Actually, I totally forgot that I have an '87 zilla that I bought from the original owner years ago with very low hours that was missing the entire top end. It was ice raced up north years ago when it was new. The top end went out, and the owner took the whole jug off and took the piston out and it sat for years. He misplaced the top end and lost it.

At any rate, that bike is an '87 and it had the factory Bridgestones on it when I got it, and I'm guessing they were original based on the shape of the bike. The only problem with the tires is that they had ice studs installed in every lug. Not too useful for me, and the tires are swiss cheese without the ice studs. But they still have decent tread if I can find them. (I took off the tires years ago to put normal tires on it so I could roll it around without tearing things up.) I could look for a date stamp on the tires if I can find them. I'm guessing they will were produced late '86 or early '87. Also, '87 250's came with a very similar Bridgestone tire, so I would sure think the zilla's did too.

You are correct Yagerzzz. I was wrong.
I went back to my owners manual that came with my 1987 and it clearly shows FACTORY stock Bridgestones on 1987 LT500 photo shoot that went into the owners manual.