Same year same model different kickdown relay?
 

I grabbed a kickdown relay from the junkyard off a 1988 300TE M103 exactly the same as my car...

...I got home and the kickdown relay part # is different. Why would that be? Would they be compatible?

The Jetronic brain part # (which I took too) was the same...so I assume it must be compatible?

Why don't you post both numbers... often parts are superceded by a new p/n. So they may be interchangeable, as in they both were used in the exact same model, but there was a change or improvement along the way and the newer part number is now what the dealer will sell you. The newer part number is not necessarily higher numerically.