Question on your Demon.
Regarding your 340 Demon. The TTi website lists your application with turn downs on tail pipes. There is no other choice.
67-76 DART, DEMON, DUSTER, SCAMP & VALIANT Exhaust Systems (Line 1I-1L)
1IH-pipe with Mufflers, Turndown, angle-cut 2.5" $ 710.95 Part # A25M WM6776
Are these the ones you ordered and used? Did you cut of the turndowns and install factory tips? Were your tips factory or aftermarket replica such as the ones TTi offers for 2.5" ? Any mods required for proper fit such as bracket or hanger mods?