Ray,
There was a guy out of Australia at www.modeltrucks.com.au who had Caterpillar C16 engines in resin. You could get them as a kit or already built & detailed. Funny thing is though, his site worked last week, but I couldn't get it to work today. Strange. Maybe it will work tomorrow. Maybe he's out of business. The engines looked nice though. He had the C16, DD Series 60, DD 8V92, DD 8V71, & Cummins N14; and he said that more were going to be offered.
Also, on the oter board, there was a discussion about someone offering the Cummins Signature engine. I think this was the predesessor to the ISX, so one should be able to convert it. But knowing your track record with the ISX, you probably don't want a model of one!