Help me add 100 hp to a magnum 5.9 on a super tight budget

My buddy runs a stock 5.9 long block with a single plane intake, 750 dp and headers in a 67 valiant. Car has 4 speed and 3.91s with 26 in drag radials. Runs 13.1 to 13.2 in the 1/4. I bet that would do it.