The 135 like the rest of the MF 100/1000 are fantastic tractors. The Perkins Gas is essentially the same engine as the diesel. They were used from 1968 - through the end of production and in some cases side by side with the Z145 by 1975.
I don"t see parts availability for it being too bad. Odds and ends like wiring harness components might be obsolete but I"m more than happy to take measurements of mine to duplicate it.