I certainly would not consider the Toyota diesel. The Cummins would be a good choice--parts are readily available and reasonably priced, the engine is very popular and well proven, light weight, compact and would be an excellent choice.
Do not overlook the Perkins engine. Everything I said about the Cummins would apply to the Perkins as well, although parts and availability are not as good as the Cummins, still better than many. I have had excellent results with all of my Perkins engines. The Perkins would also be considerably cheaper than the Cummins, at least by my experience.
