Oil leak behind the dash? It's probably the original copper oil pressure line that has a fracture in it and is leaking. Quite a common problem with the mechanical oil pressure gauges with copper 1/8" lines. This is our Nylon oil pressure line kit that replaces that leaky copper line. Vibration resistant Nylon. Comes with nuts and furrells to connect both ends from gauge to engine.  When restoring your Tractor, always change out the original copper oil pressure line with our new Nylon OPS kit.
NOTE: Remember, this is a Nylon line. Keep this line away from exhaust manifolds or exhaust pipes. It can melt when cooked!