The rear axle of the 1957 Imperial is braced on both sides to keep it from "walking". This engineered unit is on all of them from 1957 to the end of 1966. The lower Division of Chrysler's ( aka New Yorker's ) does not have the two piece drive-shaft and this assembly.
But you can swap the rear gear ratio to be more like the 300 series. The 3.23:1 is a better street performing ratio than 2.93 any day. This will help to move the tonnage from 0 MPH to ...
Keep the single four barrell carb that you have. Do raise the Compression to an 10 to one as the 1958 engine, with an Cam Assembly much as an today's RV spec's Good lift, not to much Duration or Over-lap. This is due to the Imperial's weight and driving needs of today.
The Seventies and Eighties Ford and Dodge Trucks used an 15" rim that can be used on your car. They even had some fatter/wider "mag types". Do remember that your wheel lugs take an 9/16 nut size ( see NAPA ).
The 1959 Imperial used the 15" wheels instead of the smaller 14's, the same 1957 rear gear ratio, the same transmission ratio and an wedged 413 cubes that weighed 101 pounds less. This new combination could out perform the older 392 engine in all ways. This knowledge of information leads to an transmission up to the 1963 - 1965 B727 which has the ability to use push buttons and be bolted to an 440 engine.
With the usage of the 1972 - 1978 440 or 400 Dodge Truck exhaust manifolds ( ... http://www.1aauto.com/1A/ExhaustManifolds/Dodge/PickupFullSize/1AEEM00081/67558/ ), the 413 or 440 now has the factory Hi-Perf center dump exhaust manifolds that will bolt in with clearance for starter's, power steering units and the steering rods or the like ( do take an moment to see the 1959 or like 413 exhaust manifolds used in an Imperial to the end of the 1966 year ). With the 413 or the 440 you can use the 1968 - 1978 4 bbl Carb and intake or, .. the 1969 - 1970 three two barrell carb unit that will shock you and others who try to follow ya. The best heads to use are the ones from 1976 with the head casting ending with "452". But then just using MoPars Porting Template ( P4120437 ) on any year of 413 or 440 will help any Imperial with one of these engine's.
Once the spent exhaust gas passes the exhaust manifolds just keep the exhaust pipe diam the same as the manifolds to the end of the infamous MoPar Tail Pipe Hook. The best 413 horse power with an single four barrel was at 360, for an 413 using items of above, you have just went above these spec's. The best 440 was at 375 with an single 4 bbl and now you also have much more if you use the above. And it mostly looks stock.
With the usage of resonator's in the exhaust system, you can have an fire belching engine and still have that country club hush-ness of an Imperial.
Rodger & Gabby
Due to the weight, the stock valves are OK, the best cam assembly for this beast is the MoPar P4286675.
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