Buy a kit to re-curve the distributor or have it done professionally.
Swap in a factory performance cam, use the Mellings version (OEM supplier) of the 068 HO cam. Advance it 4 degrees, use a decent quality timing chain set. Changing the cam/timing chain set can be done for about $200 and weekend of work, plenty cheap enough for a good performance boost.
Don't cut off the tailpipes at the mufflers, the only thing you'll gain is carbon monoxide poisoning.
