Actually it is true. However, on any car I value, changing the oil ever 3k miles with good synthetic and a good filter is the way I will go. I don't know much about that "double filter" setup, but I do know of a filter they make that is in fact good to around the mileage you mentioned. But you HAVE to run synthetic that is rated for that much mileage, and even then...well I wouldn't do it. *I used to work at a couple different Lube shops, and have heard all the oil myths. some are scary...*
Similarly, never run long lasting synthetic oil without a good filter. Doesn't matter how long the oil is said to go, if the filter isn't any good after 3k miles, the oil will follow in close pursuit.
Anyway don't think that helps this topic much, so in light of that....NICE CAR!! seriously, thats a beautiful find. I guess I'm a sucker for blue.