If buying the right parts with correct dates makes you car more valuable and more factory correct, buy 'em if you can afford to do so and sell the stuff you have. Some of these hard to find parts, like a CX or CY trans for example, don't come up for sale very often, so you have to snag 'em when they're available.
Anybody have an MO 512 block Dec/Jan date? I have a #3904351 L71 block with H 29 6 date to trade
