Did you mean COC6503A86? They were built by Chrysler in 1968.

Try this auction listing:
http://www.ebay.com/itm/Chrysler-Gear-Case-Housing-Lower-Unit-3-5-hp-1968-Outboard-Model-301-Viking-/171102894567?pt=Boat_Parts_Accessories_Gear&hash=item27d686f9e7&vxp=mtr

Thanks for your help. Looks like that is perfect.