Yeah there are 4 different bonnets between the early KE3x's and the late KE55's. One main design for the KE3x's, updated in 1977 and the other for the KE55's starting in late 1978, updated in 1980.
KE3x bonnets have vents with vertical lines and a central V while the KE55 bonnets have horizontal lines with a higher power bulge. Early and late KE55 bonnets also have different chrome strips.