I put mine on 4 stands on a arms and rear axles. First i made sure the 4 stands wehre the exact same height. My garage is as level as can be (meaured with string and level). Made sure all doors opened and gaps measured the exact same as when on the floor. Trunk, hood, all of it. Then welded em up. No problems.
I used a tow truck for mine since I don't have access to a lift. Just picked up the rear about 4 feet until the front bumper was almost touching the ground since our trucks all pick up by the tires and left the front tires on the ground. Lifting the car at an angle didn't make any difference since you would have to get close to the tipping point before the weight changes. All you have to make sure of is that you don't have the car twisted... just make sure your fronts stands are the same height as each other and your rear are the same. they don't have to be the same front to rear.
To sum up, it does not have to be level, it just has to be equal and have the weight on the axles.
To sum up, it does not have to be level, it just has to be equal and have the weight on the axles.