Each one can scan 23 TKey/s using CuBitcrack or the whole 16 Tesla's GPUs?
I don't think there's a method to crack puzzles fast, unless of course if you have public key.
All you can do in my opinion is to search randomly in puzzle 64 using 16 Tesla's GPUs with the speed of 23TKey/s and hope for luck to get the private key.
if you perform 23 TKey/s
you need modified bitcrack and my list
that will take 7 days to find