[Lionel]

Have you had a chance to read this parts manual?

They all seem to call for 2 parts of each, (connecting rods, piston) so opposing cylinders?

https://www.casecoltingersoll.com/d3/manuals/PartsManuals/Massey%20Ferguson%20300%20Series%20Parts%20Manual%20651%20626%20M91%20watermarked.pdf