August 1964 ~ 1964 Dodge Dart GT 'The Red Weenie'

Exhaust upgrade??? Hard to believe it used the stock 180 HP single exhaust pipes and put out 240 HP ???

The 65-67 273 Commando/Charger needed pistons, 10.5:1 plus cam/4 bbl and exhaust to get 235 HP

Really doubt "hollowed-out' low back-pressure Muffler" alone would do it...