I second the notion of mechanical upfit for longevity. I work on these things daily, and being a gearhead, there is just nothing more disheartening then seeing an engine with strong internals with a fuel system that just doesn't deliver. I sinceraly hope that the common-rail doesn't turn out to be as common as the VP-44 and the Caps pumps have been. It really stinks, because when these things work right, they really do run good... driven a 330ISC lately? Likewise, when they don't, you just have to wonder, BTW, Bosch, Cummins, or not, you can thank the EPA for most of this.
P. S. The ISB is still being made for the industrial market with some very respectable and interesting HP/TQ levels... check them out.
Russell