Yeah do yourself a favor and forget the leghorn for meat. If you want alot of eggs those girls are tough to beat.
As for duallies and meat I would recomend the NHR. Only because i have no expierennce with the rock and the NHR tend to have better availiblity and are somewhat less expensive then Delawares. I butchered and ate my NHR roo today. He dressed out at 7lbs.
He was hatched last June but I could have butched him at 21wks at and had a 5+lbs bird in the freezer. The NHR grows faster then a pure cornish but wont have the breast meat like one.
Aside price and availibity the same can be said for the Delaware as the NHR. They grow fast, get big and meaty, but have calmer quieter dispositions.
If you want a pure meat bird look into the red or black broiler. No experience myself with them but I hear good things. If thats a corinshX, Im not sure.
As to houseing and feeding, you should be able to keep them all together. I would recomend feeding them all, hens too, a high (+20%) protien ration until you stock the freezer. With duallies give them a good 20wks and you'll have meaty birds. Most of your hens wont be laying yet at that age so you can switch to a layer ration after your meat birds are meat. Granted this isnt the cheapest route to go because your laying flock doesn't required (it won't hurt) that kind of protein in their diet. I cant say you will get bigger hens that can lay bigger eggs because of the higher protein diet either. Maybe.
