Paul --

If I were to do it again, I'd check the forums at a conversion site like www.toyotadieselmadness.com for some leads. Those guys perform this sort of work on Land Cruisers and pickups and I've seen several talking about ordering half-cuts, so maybe their sources could also deliver Isuzu parts. I seem to recall that there was a favorite/reputable source they were recommending.

Failing that, most japanese performance-oriented message boards deal with importing engines on some level and could also provide some leads.

You could also explore the Olds diesel option (as discussed on this forum) or, as I am contemplating, the Isuzu 4BD1-T found in the NPR trucks - there is now a chevy small block adapter package available for it, opening transmission options up considerably.

Good luck, and keep us posted.