had the same problems a while ago.
singel phase ramps can be just as fast as 3 phase, at the end of the day the speed at whitch the ramp lifts is a product of gearing / mecanical or hydralic advantage and power avalible to the system. you won't find meany car ramps with more than a 3HP 2.2 kw motor be they 3ph or 1 ph but a 2 ton lift will be faster than a 4 ton not that that really matters much anyway.
as for what your bolting it down to
a cattel shed will more than likely have a 150mm ( 6" ) slab , you'll need to drill it to confirm this it may be mesh reinforced but there again it might not be, a metal detector will answer this.
i would have no issues working under a ramp on a 150mm mesh reinforced slab.
if your floor is below this spec like mine ( floor in mine is 125mm not reinforced and sh!t concrete and there is a join in it )
1) DIG out a cubic meter hole below eaxh post and fill with ready mix , sounds good solution but it sucks the two blocks arnt joind so may well allow movement.
2) dig out a cubic meter below each post then a trench ( width of holes ) 1 meter wide and 300mm deep joining the two holes together, reinforce with mesh and fill with ready mix, problem with this is landlords don't like you cutting holes in there floor
3) buy ramp with steel H frame bolt it down and bolt the ramp to it. jobs a goodun