Oil fouled like a big dog.
More than likely at 170K on it you can throw a small cat between the valve stems and guides. :B
But then again it's a big block with small skirt pistons so it could be coming from them too.
I would NOT use rids in a big block under any circumstances for towing. I would use plain old AC plugs and if you really want to get fancy you could side gap them like Ben told you to do. If you do side gap them you will more than likely get more mileage out of them before they oil foul.
In any event, it's a big block, they use oil.
