Hi Guys loco looks really good and will be well used on my layout. There is a good Grids book out - a couple of years ago but as noted with 135 locos from 3 factories and several versions from Doncaster it would have been a massive investment to tool for all sorts of changes . I understand 3 cab designs, two horn covers , two grill choices on main grill plus later EWS mod at No 2 end on cant rail grills , buffer shape and cowls - with three versions of cowl - each getting less and less! Head lights, front handrails, marker lights, cab handrails give a mass to be going at. The recent range of independent operators give rise to even more livery variations... plently of scope for modelling
Robert