My Chevelle dosn't have much of a turning capability. By this i mean my car makes wide turns. I can't usually clear u-turns on the first try. When I jack up my car and turn the wheels all the way, it seems a part of the backing plate on the disk brakes almost hits the lower a arm(very close). If i were to buy a better steering box for more turing...wouldn't it the same as before if my a arm were to hit? My friends 71 has drums and he has really good turning. Is it just me or is that normal?

Adding disc brakes does make the front track 1/2" wider on each side.

It sounds like you did the B-body spindle swap. If so, this is one of the negatives of it. You can either get a Caprice 9C1 box or one from a Jeep Grand Cherokee. Do a search to find the right ones, it's been discussed.
If you didn't do the swap, I'd say you have other issues.

Changing steering boxes will not regain the turning radius lost during a tall spindle swap. The above boxes have a faster ratio but it doesn't change the steering arm geometry which determines turning circle. The tall spindles have a longer steering arm, that is why the turning circle is reduced, there is no "bolt-on" fix for it. Either change spindles or cut off the steering arms and weld on shorter ones (NOT A ROOKIE MODIFICATION---SHOULD ONLY BE DONE BY EXPERIENCED CHASSIS BUILDERS WITH VERY GOOD WELDING ABILITY). You could also find different pitman and idler arms to change the steering geometry or relocate the steering box and idler arm mount, again this is not a rookie move.

I don't know how to distinguish an A from B body spindle, but if they were B body, If I were to change over to an A body spindle, will my turning radius improve? By the way, the disk brakes were already on the car when I bought it so i don't know if a previous owner did the conversion or what.

Do the steering arms bolt to the spindle or are they cast as part of it?

Yes, if you have B spindles going back to A spindles will correct the turning radius issue.

Lets find out what you have, can you take a pic of the front and back side of the brake/spindle assembly?

I'll take some pictures and post them.