I bought an old tiller with a 4 cycle, 5hp Briggs and Stratton motor. It is a Montgomery Ward tiller, but the serial # is scratched out. All I can make out is that there are 2 digits before the number L, then a space followed by 390 (another scratched out letter or number) then latestly the letter B (_ _ L 390 _ B). Any help would be greatly appreciated! Thank you, Melodie