I am not an expert on Super 99s.  But as far as I know the Super 99 had 2 diesel engines.  There was the 6 cylinder and the 3 cylinder General Motors.

The 6 cylinder is an Oliver designed engine.  The castings for the engine were made in Charles City and sent to WAUKESHA where the engine was assembled and returned to  Oliver for mounting into the  tractor.  When looking for parts the main thing you have to tell your parts man is that the tractor has the 6 cylinder engine, not the GM.

Bill Brandt