Pinder,
I also like the solid feel of that cast screw on cap, but I like "original" or "correct" better !!
So, my blue car will stay bayonet.
And, it appears, my Anthracite car is WRONG.
I can't imagine what would have occurred (switched valve cover and oil fill cap) to make that happen since I bought the car from the original owner with 78k miles on it. The car had not been "messed" with, it just needed lots of deferred maintenance. I guess just about anything can happen in 46 years.
Can you tell me the VIN of your '70 car? Or at least the month/year of manufacture?
It sounds like both of yours have "correct" oil fill caps.
Thanks,
Mark