As I've said before, I love my home-made ramps. Super stable & indestructable.
Get some 2 x 12" lumber.
Cut the first piece 48", the second piece ( on top ) 42", the third 36" etc..
Mine are stacked 5 high, which gives me the clearance needed for most jobs you want to do without a lift.
Also, nail a piece about 3" wide to the end of the very top one, to serve as a wheel-stop.