I have a problem with removing the top few inches for a crop application. That's good topsoil that you're taking away there and even better after tilling in the organic weeds. In some areas the topsoil is only a few inches deep.
If you have written off this season already then I would simply till the soil(Disc, plow, cultivators, rototiller, whatever) repeatedly to kill the stuff. The fresh black soil won't stay weed free for long nomatter what you do so get a fresh tilling in before you plant your pumpkins and hope that they grow faster than the weeds.
Now if you're task is to remove the material to make way for a building or some other non-crop use then I have used the box scraper with very good success. Depending on the distance between graded area and spoils pile I will either drag the full box to the spoils (short) Or scoop up the scraped material like 3RRL and then use high speed to scoot the spoils to a distant dump site.