The springs, shackles, and lower shock mounts just bolt on with basic hand tools, it takes about an hour per side. The upper shock mounts from the kit I bought don’t work with my particular trailer, so I’ll have to buy some others and weld them on.
I’m planning to run the Michelin M8008’s in 225/75R15. They are only about an inch taller than the factory tires but are 10 ply and very good quality. My goal was a 2” lift with more travel and a better ride. If you want 4”+ lift you’ll need to do a spring over conversion instead. I didn’t want the taller center of gravity and I’ll be able to get this trailer in anywhere I want to take it with the extra clearance I have.
Keep in mind even a 6x12 isn’t an ultralight Jeep trailer and getting it into really technical trails could be a bad time. Think about muddy, off camber, downhill 2 tracks with 2000+ lbs pushing or pulling you, and not being able to turn around.