You can't beat the 3 cylinder Perkins in the 245 and 1700 hours is barely broken in. My 65 135 diesel can sit all winter and start right up like it was running the day before. If your 135 is a diesel you'd already know this. As legendary as the 135 is, the 245 is an improvement on it. If the 4000 had the engine rebuilt, what else is needing to be serviced and/or repaired? Same money and one is original with low hours, never been apart vs. one with a rebuilt engine and most likely a lot more hours. The 4000 I think is a little bigger if you needed more power but from what you asked, the 245 hands down!