441X came on trucks, 1969-72, and some 400 small blocks. I have had 441x's and the valves were 1.94-1.50 factory and compaired to a 441, they appear the same, I have had both heads, they are good for mild use. Both heads are the same casting, same cc chamber, no difference between the two, except steam holes for 400's.
I have had both, unbolted from factory cores, and have never seen or noticed any power difference. The 461X is the only head # that ends with an X, that is a performance Chevy head. Check for cracks around the exhaust seats.