Let's see how close I get: ACF well car (SP/SeaLand, the original) - 1977 ACF Double Stack - 1981 Budd Lo-Pac 2000 - 1981 Gunderson Twin-Stack - 1985 Thrall Lo-Pac II - 1986 Trinity Backpacker - 1987 Gunderson Maxi-Stack - 1988 I could continue, but why? All of the above is from The Model Railroader's Guide to Intermodal Equipment & Operations by Kalmbach.