I've thought about this a bit with mine.
Getting a motor isnt too hard, though there are some questions around what you'd do with the transmission. Most EV's end up with a single speed reduction of somewhere around 9:1. You could use a manual trans and lock it in 2nd/3rd to get the right reduction, but thats a lot of weight.
I've seen a conversion using a Tesla drive unit mounted sideways where the transfer case would go, with a new set of gears made to replace the built in reduction (because your driving the stock axles). However when i did the sums the resulting gear ratio still wasnt right for a P38, seemed better suited to a 90 with bigger tyres etc. Tesla bits are also mega bucks. A LEAF motor is a grand, Tesla one is 10.
The most appealing setup I've come across recently was using the hybrid gearbox from an GS450h... With some simple mods it can be run as a standalone motor, is pretty powerful, and costs about a grand. Theres also a 4wd version with a transfer case on the back, though those are significantly rarer!
The big sticking point for me is batteries. My LEAF has 30kwh pack, about 25kwh usable and that gets me 75miles or so on a decent day (faster motorway driving etc) i suspect 25kwh in a P38 is going to get 50miles, or maybe even less, just with the relative inefficacy. Thus for it to be a useful vehicle i recon it'd want 60-70kwh minimum.
a 30kwh LEAF battery costs around 3 grand. a 60kwh LEAF pack is more like 10. 75kwh Tesla packs are 13+ which feels like a lot of money to be pouring into an old landrover.
Maybe in a few years battery prices will come down a bit and it'll look more sensible!
People have been saying battery prices will drop for years, still hasn't happened.
Doubt it ever will to be fair.