The very first reissue of the old 027 passenger cars from the 2400 series was the TCA bi-centennial set in 1976 with the U-36-B locomotive painted somewhat different than the stock cataloged U-36-B Lionel had been offering 2 years prior. The first reissue were true postwar reproductions with metal trucks and open vestibule door windows. Apparently Lionel at that time had a hard time assembling the cars and missed the July 1976 release date. I also heard the some of the tooling for the car bodies was damaged during this run. These cars ( 1974, 1975 and 1976) were made in true postwar fashion with the already mentioned metal passenger trucks, roof ventilator roof screws, old style lamp brackets, and heat stamped lettering.
Also cataloged for the first time in 1977 was the Amtrak Lake Shore Limited set which included an Alco style diesel and 3 passenger cars. The new cars were in the 6400 series now and considerably cheapened from the Bi-centennial edition. the trucked changed from metal (old style postwar with mechanical couplers) to a all plastic truck frame and couplers. Lighting changed to plastic bulb sockets from under the car. The functional ventilator roof screws are gone, and the vestibule windows are now filled in. Lettering is now pad printed instead of heat stamping. A 3 car add-on set was also offered.
After about a decade of no production on these cars, in 1987 the cars reappeared in the 16xxx series. First was the brown Pennsylvania cars from 1987, built like the earlier 6400 series cars. Then the floodgates opened. Many colors and names became available in the fallowing years. Lionel Lines in emerald green, Amtrak again like the first 6400 series, Northern Pacific, Union Pacific, like the 1950 anniversary set, New York Central, Quicksilver set (fictional, but similar to a Texas and Pacific livery,in the earlier 6400 series), and several others already mentioned above.