Can this be identified by just looking at it? It is back in car now.
I do not think there is a difference in the pilot hole for a small block or big block. They interchange.it appears to be a 168 tooth, dual converter pattern flexplate for a 400 small block. Note the counterweight. Big block 454 looks the same but has a bigger crank diameter.
FYI yea al is correct. The crank flange diameter is the same, 3.58" for two piece cranks. SB one piece cranks are a 3.00" flange. Even though they are the same there are different flexplates according to the GM performance parts catalog. I forget do 454 flexplates use the external weight like a 400sb? The one difference I saw in the two was that the BB flexplate didn't have the dual converter bolt set up.I do not think there is a difference in the pilot hole for a small block or big block. They interchange.
You are correct, that is a 168 tooth external balance (IE: 400SB/454BB) flex plate. That also has dual pattern torque converter mount.