A place for more technical discussions. Please make sure you post in the correct section on the site, this way it keeps the site tidy AND ensures you get a more relevant answer.
The Vitara 1.6 would be the easiest. You could get an 8v on a carb and do an SJ conversion which would negate the need for most of the electrics. The speedo works off a sensor on the transfer box and I don't know what it needs to work though.
If it is from a donor vehicle made before 1992 you could lose the cat but a Jimny engine is better waterproofed with the coil packs though.
To fit a diesel engine - how does an SJ413 gearbox fit on a Jimny I wonder? I say this because the concersion plates exist for all manner of diesel engines - Rhinoray can sort them out.
On that note, perhaps a call to Rhinoray might assist. He might want to develop a new product and have you as his guinea pig. You don't know if you don;t ask!
Otherwise I'm sure he would not mind if you picked his brains on the subject. There might be a reason why he hasn't done it already.
Kirkynut
The underdog often starts the fight, and occasionally the upper dog deserves to win - Edgar Watson Howe.