I have a bunch of the low nose 38's and 40's. As Jon pointed out the lack of steps to the cab, the extremely large sand filler (one of DA's first detailparts was a replacement) , the glob of plastic in the first stack from where plastic was injected (another of DA's first parts was a stack), and the the tab type dropstep on the anticlimber.
The biggest downfall was the fuel tank which did not resemble an EMD and had the slot in the middle for a screwdriver to take the shell off (right now I'm experimenting with Kato SD40 tank halves to see if I can use these to get a better fuel tank, there is alot of metal there to file down and I did profile one to the correct profile but it took a long time) , other than that they were the first to use 'can' motors and I can tell you they are early can motors, it's a great runner if you replace the motor. You don't have to do this Glen as they put it on a better frame.
SmokeyValley handrail kit #5 was for these units.