http://evalbum.com/type/LAND
I often pop into that site to check out the latest conversions. There are some really interesting ones on there and you can learn a lot by following the builds on that site or from the links from them.
Range is always the limiting factor to converting a car to electric - fine if you just poodle around town, but if you want to go distances, you have to expect long fill up times and a lot more frequently than filling a petrol/diesel tank.
The main limiting factor for doing a conversion though is cost! The parts are hugely expensive. The motors and batteries are not cheap. The conversion is not simple either. Obviously the heater will need to be electric, but anything running off vacume - ie brakes need adapting and bits buying. Donno if a 76 Series is servo assisted. You definitely don't have to worry about altering the security and ABS systems on an SIII !
I recon the Freelander 1 is about the best Landie to convert. It has an almost 'normal' FWD setup and a rear axle driven via a PTO from the front with a viscous coupling bolted under the car in the middle of the props. Most Freelanders are 2WD anyway having had the props removed - so bolt up a motor where the VCU goes to drive the back axle and you got yourself a hybrid! LR did produce a (or a couple) of prototye hybrid on the F2.