I don't know if the rod I have is for a C or not. I had electric start added to my crank-start '42 B about 30 years ago. The dealer installed a starter rod that went through a small support bracket on the upper side of the battery box, on the end of the box nearest you as you set in the seat (as I recall). It was NOT down low by your right foot as I have seen on some Bs. It was more like the elevation of the choke rod but on the starter side.
This rod is 1/4" diameter steel stock with an overall length of 29.5". The starter end has a 90 degree bend that is about 1/2" long (after the bend) to engage the lever on the starter. There is a small hole near the end of this bend for a retaining cotter pin. The hand end has an almost complete loop of 1-1/2" diameter. There are two slight angles in two different planes (one vertical & one horizontal) between the two ends. Both the bend at the starter end and the hand loop are in the horizontal plane. I no longer have it on my B so I cannot get an installed picture for you. It is a relatively simple thing to make though.