ON my 71 I am redoing the front end, bearings, brakes, rotors, etc. IN doing so, I accidentally let all the brake fluid drain out of my front reservoir since the calipers are off. Does this effect the rears. I know they are separated, but was wondering if an empty front reservoir would effect my rear when I get the calipers on adn have to bleed them again.

It probably didn't unless you pressed the brake pedal when the brake lines were off. But I'd bleed the rear too, just to be safe.