Agree, All kinds of myths and misinformation. I will say that you will not find a 397010 block as a 307, since a 307 does not have a 4” bore. Also, I could not make out the TBM as someone noted, but the “T” means it was in a truck, however it is not a 1970 307, if it is a 397010 block, it will be the 1979 truck 350, which is also correct for the square pad with the stamps.No there are all kinds of urban myths about the 010 block. Some folks swear it's 10% nickel. Not true. The one true thing about it is there were probably more of that casting number built than any other because it was around a long time and was used for all kinds of engines. 302, 307, 327, 350, 2 and 4 bolt. Not sure if it was used for the 262 or 305 V8's like the ones in the Monza's.