Panzerjaeger-Triebwagen 50 (Compatible with Lego)

This is a german "Panzerjaeger-Triebwagen" from WWII and a kind of weird project. Lacking any modell railroad i decided to build something that runs on the Lego tracks. At ebay i got a flatbed railroad car and constructed the historic "Panzerzug" to match.
I have no clue what scale it is but 2 Lego mini figures fit (barely) inside it.

The hull consists of two identically and rotationally symmetric parts plus the top of the cabin. Originally i planned to glue the main parts together, but