That's an awful lot of shot for light target shooting. Probably 1 3/4 ounces of 7 1/2 would be the ones to order.
Bill it would take a hell of an 8 gauge to fire 3 ounces, that's a 4 gauge load. A big heavy one with 4 inch chambers might do it, about 2 1/2 ounces is pretty standard over in the UK.
A load like that in this gun would kill at both ends, and probably not do much for the gun itself either.
Even with these heavy charges I doubt you'd get more than one quail at a shot. That's not what these guns were made for, they've got a lot of choke and were made to shoot long range for the most part.
Destry