For Sale is a good used McCulloch connecting rod.  It is P/N 47903.  It is the heavy duty type, does not have the oil slit.  Still   Very nice rod, a must have for the serious racer, this will upgrade the other weaker rods used in the earlier models. 

It will fit:

Mc Kart 5, 6, and 10 Mc 90 and 91 models.

Be sure that this will fit before you buy it.

The photo is a photo I have on file, since I have several you will get a 47903, but it may not be the one in the photo, some were copper colored some were not.