Why so specific? I kind of understand kind of why you are looking for this stuff, and I wish you luck, but its none of my business. If you are not able to locate these specific year cores.
I store my numbers matching block and transmission in my basement, so I don't live in fear of breaking them while having fun with the car. In over 40 years of having the car, no one has ever tried to see the number pads/numbers on the car. Are you going to show the car in a judged competition?
Absent the original numbers matching items, looking for a one year only issue of non-matching numbers parts makes your build harder. Besides, who's going to look, and if they do, the numbers don't match anyway?
