Nuttin fancy. 2x4 legs and frame, 1/2 inch osb shelf. I want to attach the 2x4's to the concrete walls, but not sure which method would work best. Powder actuated probably won't work as this is a 100 year old foundation. I'm debating between 3/8 x 4" sleeve anchors and 1/4 x 4" Tapcons. Any preference or other suggestions?