In the mean time, head over to
www.mymopar.com and see if they might have the one you need, for free download. You can tell a "built" system from a "factory" system due to the type of hangers and the way the bends are done, once you know what "factory" looks like. I like having a physical parts book to turn pages in, but the digital versions can be good too, once you get used to dealing with them. Just can't put your finger on one page, to hold the place, as you look for something else. But after dealing with OEM digital parts databases for years at the dealership, I kind of got used to the digital versions.
Personally, I would suspect a factory dual system for Imperials MIGHT have been available, but I suspect the OEM factory system would have been a single exhaust. By that time, with the low-compression ratios of that time, a dual exhaust would not have really been needed. As it seems that the factory single exhaust system had larger pipe diameters than what the Fuselage Cars had on them. PLUS the suspected production cost advantages of a larger-diameter single exhaust system over a dual exhaust system. So it would have been only Police cars and HO engine options which would have had factory dual exhausts, by that point in time.
The orig Lean Burn cars were "Non-Catalyst" in 1975 and 1976, plus the FLEET engines Chrysler sold back then. 318 2bbls, 360HO, 400HO, and 440HO. The last three would be for law enforcement or consumer special orders and had full "real" dual exhaust systems under them, sans cat converters, in the 1976 or so model years. The 318s would have been for more administrative-use municipal vehicles, I suspect. Back then, too, any vehicle with catalytic converters were banned from Federal lands, due to their very hot exhaust system items (the cat converter itself) and related fire hazards. Cars and pickups (under 6001 lbs GVW, back then). As things progressed, the factory convertered systems had "environmental heat shields" under them, as Chrysler was the only company to sell HO engines with DUAL cat converters for real dual exhausts (not a single converter feeding into a dual-outlet muffler, as GM did) until the 1981 Chrysler Newport/NY and Dodge St. Regis cars came to an end. There were also underbody heat shields for the floor pan, for the full length of the passenger compartment floor areas.
From my observations, years ago,
CBODY67