As far as I know, the pans are the same capacity. There may have been a windage problem in the '67 that was cured by filling it less in '68. I would assume, also, that this would require a slightly longer dipstick in '68. If anyone has a stock '67 and a stock '68 car, this would be an interesting thing to look into. (Banshee, you've got at least one of each, right?)
I recall that during the oil embargo in the mid '70s, oil filter sizes were cut in half to save on the amount oil put into cars as they were leaving the factory. I doubt this was considered as a strategy in '68, though.
