Did you want an engineering cert for the engine swap? not only does the zook not handel well with a heavy front (what iv heard) but its very hard to engineer it after exceeding a percentage of weight over the original engine (what i know) was talking to an engineer today about it.
I started looking for engin options about 4 months ago and for the first month was dead set on diesel for EXACTLY the same reasons you are, even wanted to run biodiesel. i reckon it was a month wasted. the best option i found was as said the 1.5 or 1.9 TD volkswagon engins. thers a company in the states that makes a conversion kit for them
http://www.rocky-road.com/diesel.html
Now uv got to source the engin, nil stocks australia preety much sums it up. importing is an option as there are stacks in USA and europe. A quote from an email i got from a couple of guy's in scandinavia
"The choice of the VW engine is do to the fact that it is a pure mechanical diesel (extreme off-road + electronics = :( and is manufactured in billions, VW Golf II/III D, TD, GTD, Passat 86 D, TD."
But after weighing up the extra tourqe and economy of the diesel verses hassels with fitting/ cost of importing/ lack of experiance in aus with other people doing it and searching through LOTS of old posts all condeming it i went against.
Also went and looked at a 2L (parently same block as 1.8L) hilux diesel from wreckers, now two people can lift my 1.6L G16B vitara engine (that i got on the wkend) with some sweat. man i reckon 4 people would struggle to lift that hilux iron monstrocity.
Would be great if you can find a way of puting the hilux donk in and making the zook handle ok, when ya do give me a bell. actually make a kit and then give me a bell and ill buy it of ya
any way just sharing my experiance over the past couple of months. PM me if you want e-mails of some of the guy's i talked to oversea's or links.