wow hear we go borrowed a sending unit from friend. Stock 40 year old unit. diffrences are swing arm on unit 1/2 inch longer after radius.diffrent ohm readings on swing of old compared to new. measuring from center of float to pickup tube. slightly over 10 ohms diffrence in same spots along sweep. both read almost same at each end of sweep. old 80.8 new 77.9 on empty old 9.4 new 10.6. where it really varies is along sweep at 47 ohms on old unit gauge reads 1/8 tank on new at 49 it reads empty.