The AMT Kenworth T600 needs a lot of work to bring it "up to 1990s spec" as it is essentially a 1969-71 W923 frame, suspension, engine/transmission, & cab interior with a 1990-94 T600 cab & sleeper plopped on top. For the era you're going for, I'd stick with the Revel Peterbilt 359 or maybe the Revell Kenworth W900 Aerodyne.