A stump that size you should be able to dig out by hand, although it would have been easier if a couple of feet of trunk were left (it gives you leverage to get the stump out).
EDIT: You're going to end up making something of a mess regardless. Tree stumps aren't just some half-buried log; they have many, often large, roots growing from them.
Pulling them out (assuming your car could even manage it, which I doubt) would cause more mess, as it would pull most of the roots out with it, tearing up the soil in the process.
Digging would contain the mess to a smaller area, as you would simply cut through the roots at around 6 inches out from the stump.
To dig them out, first dig out all of the soil to about a 6 inch radius around the stump, going down until you hit thick roots you can't simply chop through with the spade.
Once you have dug that trench around the stump and located the roots, you need to excavate a little around them so that you can more easily chop through them. To cut the roots, use loppers (assuming they are under about an inch and a half thick) or a cheap pruning saw or wood saw (don't use a good saw, as the soil will blunt any saw you use).
Once you have cut through all of the horizontal roots, start trying to rock the stump. Use a stout iron or wood bar to lever it if you can. This may be enough to get the stump out on its own, and if not, you should be able to work out where the remaining roots are based on where the most resistance is. Dig out some of the soil from beneath the stump until you find the remaining roots, and cut through them, then lever the stump out.
I've dug out stumps this size solo in 30-40 minutes before using only a (sharpened) spade and an old pruning saw.
I did leave about 2 feet of trunk on them for leveraged, though. If your stumps are cut low it will take longer, as you have less leverage. Time taken will vary based on the species of tree, too, as some trees have harder roots, more roots, or more roots going directly down than others, so will be harder to dig out. It will be easier if you can get someone to help you, though.