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Might just hire it out?Lot's of people with small tractors and a tiller could do it. I've got a 5 footer I tilled a lot of ground with and a 28hp tractor, takes several passes for a yard quality job. Someone with a good old Howard tiller would do a better job than someone with a lesser tiller, like a king cutter.
I think you can rent one from farmers equipment on Hwy 20 for $150 for the weekend, or something like that. Used ones I have seen go for $500 and are beat to hell. I know it would be a major pain for you but id line everything up, maybe your project and a neighbors and rent it...
Use a plow attachment first to break up the compact soil, then take the tiller implement to it followed by a rock rake. You'd be surprised how many good sized stones float to the top.