The Airstream motorhomes HAD an Isuzu diesel in them back in the early 80's, here in the States. From what I have learned through the forum, Airstream used the Chevy P30 chassis and fabricated everything else to get the diesel into the chassis. Believe I've read that in order to have the engine turbo-charged, Airstream even went so far to do that to the Isuzu as well.
So, if you're able to locate an older diesel Airstream that's being parted out, sure you might be able to get some of the parts required. Maybe even locate parts online. No idea where to start to be honest, but do know that you're definitely in the right place (Airforums.com) to find out what you need. Have you read through the moho engine forum yet? May be able to find out exactly what you need there.
In fact, this thread may be better off in the Engine section of the motorhome forum.