I know the wiring harness for the nav system in the LX470 is different between these two years. While not really an answer is it suggestive that you may face issues.
My suggestion would be to look up the connectors in the FSM on both and see how different they look, then take a risk maybe.
I face the same issue with a driver's seat that I bought with a memory control box in it going into a 98 without seat memory. I decided just to plug it in and give it a smoke test and see what happens. The connectors look identical, but there must be data going to the position control box....so who knows...
Back to your instrument cluster, my 2001 LX470 has a very nice dashboard and I suspect it probably would have a better chance to fit into your truck. Here's a photo of one: