I always wanted to build one like this, my plan was to bolt the motor right to the transfer case and call it a day. I don't believe however that the gearing would be nearly low enough.
The costs are just crazy too. You can get a used 350 block, and all the parts you'd need for 1/2 or less than to go electric. Maybe someday electric parts will be cheaper... once there is a 'used' parts market.