Actually, that's not quite correct. You would want a lower unit from the 1957 & 1958 Johnrude 35s with the SINGLE WALL exhaust housing, and 1960s era 33hp models (28hp models might work, too). Avoid the lowers from Johnrude 40hp models, as well as 35s with the DOUBLE WALL exhaust housing (looks fatter due to a second outer housing). Easiest way to tell them apart is the ones that WON'T fit will have TWO tubes coming out of the water pump housing.