Hello, I have a Cub Cadet SLT 1554 with a 54 inch deck. I changed out the blades on it Yesterday and noticed the belt was getting bad. The manual I have calls for a number 754-04083. When I search for this belt I can find it on several sites. I am confused because some sites list it as a 136 inch belt and others list it at a 138 inch belt. Does anyone here know the correct size? Thanks in Advance...