How to size electric motors for a 7,000 pound utility vehicle?

This idea is a little past the whimsical stage - now testing with reality. I would like to make a vehicle similar to what is pictures. It was used in WW2 and the Korean War - maybe some time after that. It is basically a small, no frills pickup truck. I have some land in the high plains desert and need a vehicle to haul stuff around - but with a lot of stop and go movement. That would hard on a diesel engine to start so often. One of the functions of the mule will be to carry a 500 gallon water tank around the property, so the vehicle, when finished and fully loaded, will weigh about 7,000 pounds. Top speed - I am hoping for 10 mph, able to climb a 30 degree slope. It will travel no more than 10 miles on a charge. I don’t think they make such powerful hub motors, but I would like to have 4 motors, one for each wheel (4WD) - possibly using half-shafts? I would like to avoid a tranny that requires shifting gears, but will consider fixed gear reduction to get the right torque and speed. What kind of motor would be used to power this vehicle?

Do yourself a favor and start with a 4wd EV chassis. Something simple, like a R&T hunter or Polaris Ranger. Badboy buggy uses two motors, front and back. Multiple motors gets complex electrically.
An EV won’t need to shift gears. Plenty of torque. Not sure if gears are available for either of these vehicles. The Ranger seems to be geared 14:1 or even lower. I need to look it up. The 35hp seems it would be enough with that gearing. It is only rated at 1400lb, but it may do the job with different suspension and less battery weight. Comes with 8 lead batteries.

I just saw a mule for sale someplace, let me look. An electric conversion should not be difficult.
FB or Ebay are the only places I look.

Polaris uses an 8.5kw motor and runs 25mph. Should do the job nicely geared for 10mph.

Here ya go