Hi the frames are basicly the same as the shorter ones ,just a little stretched iso mounting bar depend on use ie ton 20ft iso carry Guinness cages or uniload containers . the frames are aprox 6 inches lower than the earlier build, this led to thebuffer shanks sitting higher than the headstocks again by about 6 inches .
headstock's are a bit different as well.
hope this helps i do have a basic drawing of this skeletal wagon ,will dig it out and stick it up