I was able to drop the lower unit without removing the powerhead but I suspect that the shift rod may have been modified in order to do so. My shift rod has the connector near the bottom so that it can be separated to be able to drop the LU but according to the parts catalog (for 1955) it shouldn’t have it. When I had it apart, I noticed that the shift rod appears to have been cut in half in order to install the connector, the groove in the side of the shaft that the bolt slides through looks like it was made with a file, it doesn’t look original in my opinion. The other thing is that on the inside the leg housing about 2 inches below the powerhead there are 4 fins that are part of the casting and it would be next to impossible to get the seal / plate / spring etc. past them in order to mate with the powerhead. My theory is that somebody modified the motor to be able to drop the LU without removing the powerhead and discarded the 6 items at the top of the driveshaft when they realized they couldn’t reinstall without removing the powerhead.
