727 casting numbers help

Ya I know the transmission is the same outside of the external balanced flex plate and/or converter. The guy I got it from said it came from a 360 and while he never said it was the factory tranny that came on that 360, I got the impression from that was the case. So if it is a 318 tranny, I need to figure out how to tell if the flex plate or converter are from a 360. Also would be interested in knowing where to look and what to look for on the converter to find out what the stall speed is.