MLW RS-10 and RS-18, what's the difference?

[cnrglen]

Thanks for the reply. As for the vent openings are you talking about the black squares above the doors? Those are car body filters and from what I've seem in photos they varied not only between the 10' and 18' but also from railway to railway. I'm figuring those were options from the factory. From what I've seen so far the only difference is internal on the locomotives. I'm just hoping someone out there can either confirm my suspicions or be able to correct them.
I'm still trying to get a decent picture of the long hood on a non-dynamic brake unit though, any help out there?