I have an Allis Chalmers tractor how do I know if it is a WD or WD45?

The WD right hand side of engine block will have a inspection plate the length of the block held on with 6 bolts, the WD45 right side of block is solid cast iron. WD gear shift lever is straight up to SN 127006, the WD sn 127007 & up and WD45 used a curved gear shift lever.