That said: your motor would probably have to be rebuilt after 250,000 miles in which case she would replace the timing chain anyway. Your rings will probably be well worn before the timing chain goes out anyway. I've rebuilt a few late 60s early 70s Ford engines in my time... You'll go through a couple of water pumps and timing chain cover gaskets before you have to replace the timing chain. Of course if you are rebuilding the engine after 200,000 miles you're going to want to replace the timing chain anyway. How many miles are on your engine anyway?