Thank you to those that have responded. Looks like the information
submitted by you readers is nearly the same. Appears the car was a show car for a dealership early on. It is an early build car. The seller was the original owner family I purchased it from 7 Yrs ago. They indicated it was promoted in the Seattle Time and Post Intelligencer news papers by the dealership as the new style Dodge Challenger. Although they were able to purchase the car they had to agree to allow 2 dealerships to use the car in their show rooms for 10 days each before they could get possession of it.
It appears they used the car to promote both features of the SE and RT.

Unfortunately they did not get a copy of the newspaper ads. The car is not an RT however it has a lot of the RT options and other add on's i.e.: 340- 4bbl/automatic,26" radiator, 15" Rally wheels, P/S,Power front disc brakes, vinyl top, luggage rack, hounds tooth interior, console, Rally dash, light package, dual exhaust/tips, sway bars, wood grain steering wheel.
Color is FJ6 Green with 6J stripe.
Very nice original car and the "Y" code is 16 as you folks noted. There is also a "U" in the "Y" box under "Build for U-C-I"

Thanks again all for the help.