Not particularly looking for a specific partial VIN stamping but rather the starting format preferably a Baltimore car. In 1970 the partial VIN was stamped such as 10B123456. I would think 71 would be something like 11B123456. I'm looking at a 71 Monte Carlo and it's stamped 19B20xxxx and sequence matches VIN - suspicious?

My 71 SS is stamped exactly as you suspect. Right off the top of my head, I think my 402 block is stamped T0902CLB, which my car is a 1D build date, then it is stamped 11BXXXXXX, whatever the last six of my VIN is, which I can't remember off the top of my head. I think that Monte Carlo stamp is suspicious.

I say suspect also.
Happen to get the casting date?