Truck Repair: V-903 C-295 Engine, cummins engine, ill look

Question
I have been searching for a 903 Cummins engine and havent been very successful. I need to replace this engine, but from what I have been hearing, this type of engine hasn't been produced a little over 15 years. What would be the next best engine to replace this 82' year old engine?  

Answer
Yes they are obsolete.I have only seen 1 in my years of working on them.Probably would be best to repower the equipment with a newer series engine depending on the RPMs required for application.It would cost a fortune to rebuild it if you replace heads.Ill look into more today on what would be a good replacement or if there is such a thing as a ReCon 903.