I made a rear subframe dolly for when I removed it on my Project 160. It works really well.
Just 4 pieces of 4x2 found at the back of the garage, sawn to length, 4 castors from Screwfix and nail/screw it together. It should fit the front too.
The subframe is still sat on it now some ...err...months later but the engine is on the bench being reassembled. I 'park' the subframe under the back of the still raised car so it's out of the way.
My method of 'lift an' separate' is:-
jack up the car to remove the wheels and slide the car lift under the body (car's too low to slip it under whilst on its wheels)
position the dolly under the subframe
lower the car onto the dolly - sufficiently manly castors needed!
undo the subframe mounts - this assumes everthing else has been disconnected already
wind up the car lift and away she blows!
Easy