I am looking at picking up a 404 (probably a 404.1) to cart back to import to OZ when I leave Germany. Ex military 404.1s in need of a little bit of repair often sell for under e500 ($700US) over here (with the M180? petrol engine).

If I bought one I would definitely do a diesel conversion. I would just buy a diesel, but you can usually add e2000 to the price if it is a diesel mog. I have heard of people doing conversions using 300D engines, and found this useful site:
http://www.ki7xh.com/dieseliz.htm

I am interested in other options though, and who has done what. Specifically things like large 4cyl Japanese truck diesels (these would be the cheapest to source and get parts for in OZ).

That thread will lead you to the main source of parts for the most common diesel conversion. it is NOT cheap conversion. Around 2500 buks just for the parts but it does include a whole new bellhousing.

If you do a Jap diesel. (In my humble opinion use HINO) you'll have to make a bell housing anyway so keep that in mind. Good luck

Get ahold of Tony in OZ. He is in need of some MB turbo engines. Maybe you can ship some in the back of your mog when you send it off to OZ. Keep one for yourself in case you can't get a Jap diesel to work like you want. Deliver the rest to Tony.

More on this at
http://www.mercedesshop.com/shopforum/showthread.php?t=145398

Thanks for the link.

Making a bellhousing is no problem. I would probably try to use an Isuzu engine if I can. Does anyone have any measurements of how large the engine bay is, and any particular quirky of the 404 which need to be accounted for?

Hi Ben. This is Bill, formerly Portalrover. The forum doesn,t recognise my username anymore for some reason so I have had to reregister.
I wanted to say that the couple of 404 mogs I seen here in OZ are extremely cramped when converted to right hand drive, and I remember you saying that you are quite a big guy, so I would suggest you be very careful when selecting an engine, that you choose one that has all the ancillaries on the left side. There really isn,t any room to spare to encroach into the right hand side of the cabin area.
Bill.