Anyone who has or knows of literature about this and if it existed (Is this a modified GAZ AA?) Sadly I am not really familiar with Russian stuff
/Stefan

Hi Stefan,
Indeed, this is GAZ-AA but I....()
Usually the German rail trucks, when not pulling cars, were paired back to back to run in both directions with the same speed: the front truck pulls, playing locomotive; the rear plays car in neutral gear.
HTH
Cheers!

Indeed, this is GAZ-AA but I consider it German. I still have to see a pic of such rail conversion by the Russians. On the other hand, many captured Russian GAZ and ZIS trucks were converted to run on rails by the Germans, in particular on the Northern sector of the Eastern front.
Apparently the kit represents German vehicles, if judging from the extended GS body boards and markings.
Only one picture to confirm what I wrote above, it is included in the kit decals:

Usually the German rail trucks, when not pulling cars, were paired back to back to run in both directions with the same speed: the front truck pulls, playing locomotive; the rear plays car in neutral gear.
HTH
Cheers!