I'm looking at a list of Railfreight Grey, Railfreight red stripe and sector 37s I would like to model. However, I am struggling to see many differences between the various class 37 chassis Bachmann have produced. The obvious difference is the circular markings/writing on the fuel tanks (see photos below). However, the fuel tanks are so dirty in Flickr photos I am finding it difficult identifying the best donor chassis. Take "Conidae" below, I have no chance trying to find a photo with the white parts, as they will be so dirty in photos.
Did any other locos besides 37507 have the similar "coloured" wheel components?
Are there any more differences in Bachmann chassis'?
Are there any rules like 37/5 always had a particular chassis etc?