The engine has 5500hrs and think could use a ring job at least. Besides just a touch of oil, the plugs don't look bad. Could probably clean them up, put them back in and see how long they stay clean.
This tractor will not have anything on it that would cause interference so I agree and think the cheaper copper core wire will work best. Just kind of suprised they want to sell me $22 plug wires for such a simple engine.