According to my chevy truck ID book WE is a 3.73 axle made at the Warren plant. It is for both 63 and 64. The 7 is the month it was made.Thus it is a july axle. The 09 is the day built. The distinguising facter here is where the stamped numbe is located. For 63 it says it is stamped on the bottom of the differential carrier housing just forward of the cover. The 64 is stamped on the the forward side of the left axle tube near the carrier housing. Hope this helps.
