Cut the grill lines part way through the block with a back saw, do not cut deeply at the bottom of the grill, but you can cut right through at the top. Use a hardwood block clamped onto the work piece as a cutting guide. Set it so the pencil line will be in the middle of the saw cut. You need a saw that cuts a kerf of 5/128" or a little more, to get a good size ratio between the bars and the gaps in the grill.

Fit the grill into the space in the cowl by sanding its sides and the curve of its top.

Give the grill its flowing waterfall shape with a drum sander on the drill press. Then fine sand to 'polish the chome'. This will remove the saw cuts at the bottom of the grill. Mark a line across the front of the grill 1/8" from the bottom, then resaw the gaps to this line.

Paint the grill mat black, make sure the insides of the saw cuts are covered, and blow out any excess paint from the cuts. Paint the bottom of the space in the cowl with the same paint.

After the paint dries, sand the paint off the front of the grill and then glue the grill into the cowl.