Oil passages and returns should be the same, left-hand or right-hand rotation. Any offset in the wrist pins within the piston and/or in connecting rod small or big end will be reversed, too. Another thing to check outside of the rotation question -- was this engine used primarily in fresh water or salt? If it was used in salt water and was raw water cooled, i.e. no heat exchanger, there may be considerable corrosion in the water jackets.
