Ok well i emailed DJ about a new design for my HD3 this is what he said
"Using the exterior dimensions of 45" wide by 24" tall and 12" depth at the top of the box and 15" depth at the bottom of the box you gross volume would be 3.67 cubes before displacements and 3 cubes net after sub and port displacements which is a little on the small end for the HD315 but would work well in your truck.
Place the port as in your drawing. Make the port 2.25 inches wide and 22.5 inches tall. Make the port 18 inches long and it will tune your box to about 38 Hz which will give you very good sql and also very loud.
dj"
I just dont know what size to cut all the peices. Can someone draw that design up and make a cut list for me so i can go to Home Depot tomorrow and start this box?