Yup, bad assumptions...The D indicates a 1968 model year engine. The casting date is WAAAAAY too late for a 1967 model year car.
Post the engine ID pad information, all of it, and any partial VINs that are stamped into the block.
Engine got swapped at some point, or else the car really was a 1968.

R.
The heads are 2843906 casting nuber heads, otherwise known as "906 heads". They are what I'd expect to see.

Now each head has a casting date somewhere on it, the last digit should be a 7 for the 1967 date of the casting.