The 6223 was used in both the 350hp and 375hp motors...the low horse motors starting in 1969 got the cast crank. My old "How to Hotrod Big Block Chevys" says the L78 crank was also "tufftrided" ...not sure how to tell about that.
And yes, the 6223 was used in all the Nova 396 and 402 applications since the low horse L-35 396 was never available in the Nova.
This link takes you to a previous discussion on the subject that should help...
https://www.yenko.net/ubbthreads/ubbt...;Number=183293
wilma