Windsor head casting number???
if you need casting numbers to tell the difference between cleveland and windsor heads......well...you have problems.
Easiest way to tell is the canted valves on a cleveland head. Second easiset way is to measure valves. The biggest valve that can be fitted in a windsor head is a 2.02 intake, stock they will have either 1.78 or 1.84. The smallest intake valve that fits a cleveland head is a 2.08 I think. Third way, if a tennis ball fits in the intake port, it's cleveland. If its a windsor, fitting your thumb in the port will be a tight fit.
An easy way to find pics is to search on ebay, search for "351 windsor heads" and then search for "351 cleveland heads", you'll see exactly what I mean.