Try this out, I think it's getting you close but may need to play with it more than I was able to.
##### Strip leading zeros
def FindLabel ( [UNIQUE_NO] ):
return [UNIQUE_NO].lstrip("0") #.strip removes all zeros
I found this here and this link explains the lstrip method. It seems to only remove the leading zeros, but if Township and Range were in separate fields this could be used two times and the two fields concatenated together to produce the result you want. Hope it helps!