On our '66 Newport Town Sedan, the factory pipes did not extend past the bottom of the rear bumper, but were probably an inch or so short of the bottom of the bumper. Which meant that exhaust heat could migrate upward to the rh backup light, coloring it a small bit, but it would wash off easily. The chrome would get a bit grungy, too, but some cleaner wax always took it off.
Many customer pipe makers, not the OEM-spec pipe makers, could use ONE rear pipe for C-bodies rather than body-specific. They can also extend past the rear bumper on some, which many like as the bumpers stay cleaner and such, but also can make them more prone to drag on sharp approach drive-ins and such.
IF you put a Fuselage over-the-axle rear pipe on a Slab, it will hang below the quarter panel. The Slabs had an upward slope behind the wheel, as the Fuselage and Formals rear pipes were more horizontal to clear their body sheet metal and rear bumper. When I put the '72 Imperial-spec Walker Exhaust replacement parts under my '67 Newport, that's what happened at the back. Had to go to a muffler shop and get them to put a bend in the back pipe to clear the Class I trailer hitch on the car. Plus to hide the pipe behind the quarter panel bottom.
The factory rear pipes also had a small hole drilled in the bottom of the pipe, at their lowest point, for condensate drain holes. Just as the rear of the muffler bottom had one too.
The TTI rear pipe exit angle and cut are pretty close to OEM. Hard to put a chrome tip on them, as a result. But then ONE single chrome extension tended to look tacky, but TWO were good. Basically, hide the single exhaust exits, but show the dual exhaust exits (for their "powerful" look).
From my "memory and use banks",
CBODY67
