I think that's right - the 103 motor was always single and the 104 was always double. They are both very solid - the 103 because it's so short and the 104 because it's double. I once had a 103 motor with 275k miles. My mechanic didn't want to change it because it wasn't acting up and he'd never seen a problem on one. His theory was that if it's not acting up you introduce risk by changing it. Bu it worried me so we did it. It turned out it was the original and it showed no real signs of wear. Most mechanics I've talked to have never seen a 103 timing chain problem. I really haven't heard about any 104 problems either, of course they're typically not as high on the miles.