Thanks for the welcome.
On further inspection, I think it's an 860---not a 861. The hood says 861 powermaster but the stamped numbers behind the starter are 860-L and 126111 (with the 26 stamped lightly and the 1's stamped deep). Which tells me it's a 1957 860.
I'm guessing it was propane at one time and converted over at some point to gas and the hood was changed. Does anyone know if there are any issues or concerns with this type of conversion?