I've done the banana guide and the upper and lower lower guide in car. I had the vacum pump off to get to them. I think the original poster needs to look at chain streatch. Someone told me there isn't much reason for the top guide to break, unless the chain is slapping against it. I would change the chain and tensioner unit. I would also look into changing the 'banana' guide. The lower two on mine didn't look to have much if any wear. I would go with an IWIS timing chain. I used a Beckley/Arnold, but I don't like their link pin. I fired mine up last night. I had it apart since December. Hope to put it on the road Saturday and maybe drive it to work Monday. I'm doing the radiator flush process.
Tom