Like PJ said, find the date code back by the dist, as well as the bock casting number. The casting number was by the dist hole on some earlier engines, and on a pad, below the rear end of the passenger side head, on later engines.
You can plug in the numbers you find & get a better idea of what engine the block was used in.
Wallace Racing's Pontiac Engine Search
The '67 YT code block was casting #9786133
, had 670 heads, and was rated at 325hp.
But the YT code was used on various 400's thru '78, as well as a '66 421.
In your case, the block casting number is critical, because YT was used on some "557" blocks, which could have a date code ending in 7. A block cast in '67, should also have a date code ending in 7. That number represents the last digit of the year in which the block was cast.
If this is true, then I suppose a date code of B067 could mean that the block was cast Feb 6, 1967, OR Feb 6, 1977. The casting number would quickly tell you which year is correct.