I was very happy when Atlas released their C424 in Reading. While nice, it lacked certain spotting features that screams Reading so I decided to add them.
Here is what I did to upgrade it:
Add cab rain gutters.
Change single sand filler hatch on top of the nose to dual fillers.
Move the horn from on top of cab roof to a bracket mounted to the front of the cab. Replace the horn.
Add fire cracker antenna.
Add C-channel between trucks and frame.
After some cad work I ended up with these:
(L-R) Sand filler hatches, new horn and bracket (actually lots of brackets), jig for making consistent rain gutters and some C-channel (needed a smaller size than available)

With the above parts, an antenna made from wire insulation and brass rod and some paint and weathering, I turned this:

Into this:





Only 3 more to go...