My magpul does not have the plate with the loop between the stock and the lower, all I have to work with is the three holes in the back of the stock. Is there a good way to mount a standard sling to it? I'm thinking of just mounting to the stock, the front sling mount under the FSB just doesn't cut it for anything but over the sholder carry, I want my rifle slung in front or on the side with the muzzle pointed downward.

You can buy the sling loop directly from Magpul.