Cannot answer your question but we are neck deep in this issue also.
We need 1Q69 or 4Q68 and are 4 short going NOS.
Longest ones are hardest.
All we have so far are 1Q69.
Another issue is some do, and some do not have lightning bolts.
The fake set we put on temporarily has them.
First pic is fake set
Second pic is a complete NOS set for a 72 BB with lightning bolts.
Note proper grey plug end boots.
Does not have the one 45* plug end like a 69 set would have.
Love this minutia.
Pics 3 and 4 a NOS early 67 set without lightning bolts. Have others but these were the only complete sets.