While I have not owned them myself, by reputation and the postings of others here on BYC, a good Ranger line is likely your best bet. As a wise poster has said, "Eat the one's you don't want to eat, breed the ones you do want to eat."
Too many of the New England Heritage breeds are basically egg layers at this point, courtesy the commercial hatcheries - without the fast growth you want, or the double breast.
For both good and ill, the CornishX is so feed efficient, so fast growing, and so provides what American's want in chicken - a bland, textureless, cheap protein - that efforts to improve the meatiness of other breeds were largely abandoned. Its only relatively recently that has changed, with renewed focus on potentially self sustaining, truly dual purpose birds that can thrive in more natural, less commercial battery conditions.
Which brings up a consideration you might want to give more though to. Sustainable, largely free-range, self replicating flocks are intended to provide a steady stock of meat throughtout the year. You are always incubating, always growing out, always putting eggs on table, and always culling birds as they "age out" - again, for table. You don't need a huge flock to maintain stable numbers and still be resilient to the whims of fate.
Without linking (again) to my
culling project, I will offer that I can incubate 12 eggs every three weeks +/-, have nine make it to size (allowing for disease, injury, failures to hatch, etc) and still take three birds a week for my own use at table. One bird is always an older hen, sausage or stew. Two birds (usually) are young males for table. I still have so many eggs most of the year that I can sell them for eating, hatching, whatever. ...and I can control numbers by deferring incubation, by deferring culling, or by culling extras, depending on my needs - while the large numbers of eggs daily means I can select just the largest (and lightest, personal preference, makes candling easier) for future generations.
Multi-hundred bird management for meaties is used to do a couple of mass rasing, mass butchering, mass freezing efforts - works well commercially, or for people with very short growing seasons and lots of freezer space. It works best when people simply order hatchery provided day old chicks (and enjoy that economy of scale) at need, rather than maintaining their own breeding flocks. If you go that route, and don't want the CX, which are not suited to free ranging, some of the "slow-growth" or "big red broiler" lines, which sort of blend CX-like characteristics and Ranger characteristics would be a better choice - with your massive facilities being free for other purposes much of the year.
