It is generally accepted that Yenko modified a number of 69 L78 Novas with the 427 engine. The total number scheduled for the conversion was about 37...though the actual number done was less.
Many of the high performance dealers back then would do just about any conversion a customer wanted to pay for...so a 70 with a 427 is certainly possible.
Fathom Green was a 69 color...not available in 1970. There are a few Fathom Green cars listed on the SYC Yenko inventory...code 57.
https://www.yenko.net/forum/showthread.php?t=125833
Hope that helps...
-wilma