I assume it's zinc pest which can happen to a potmetal part if impure materials are used and/or the mix of the alloy is incorrect.
73 U code cars don't have and never have had anything but single snorkel trap door air cleaners.
Meanwhile, here is the decoding thanks to Nick, with the A07 package info added by yours truly, Johnny Dollar.
OP (@69monaco ) — could you please mark the car as “SOLD”?Details to follow!
The U code wasn't available to the public in retail 72 or 73 Plymouth Fury models as well. So I would assume the same would be true for the Polara/Monaco, however 72 U code 440's have a dual snorkel, the 73 is a stand alone with the trap door single snorkel that is shared with the 73 340.U code 440s were not available on Polaras and Monacos that were not patrol units at least in 1973. All I am pretty sure of is that T code 440s in 1973 had dual snorkels. I had a 73 Monaco wagon so equipped from the factory and other Dodges with T codes also got that air cleaner from my observations for 73 models. So from what you are saying, the purported reason for the dual snorkel doesn't hold up for 73 then, but maybe the carryover mentality prevailed nonetheless.
I have the factory "Dodge Police Cars 1973" Brochure, and on the inside first page it says that the 440 engine in patrol Coronets and Polaras is "available on no other Dodge models". I assume that means the U code.
FYI unless I'm mistaken if this post gets marked SOLD the thread will be closed to new comments. Is that what you want?
Suggest you start a new thread, if you have not done so already, to document your journey with this car. I could move the posts from this point on to that new thread if you'd like. If you have a new one already what is the url?
I can,t change it anymore , don,t know ; sometimes you can/sometimes not..
FYI unless I'm mistaken if this post gets marked SOLD the thread will be closed to new comments. Is that what you want?
Suggest you start a new thread, if you have not done so already, to document your journey with this car. I could move the posts from this point on to that new thread if you'd like. If you have a new one already what is the url?