I have also been assembling some intermountain freight cars. Building
them is sometimes frustrating but the end result looks good enough to make
up for the hassle. Generally I just build them as is but I do paint the
underside of the boxcar shell black so it matches the frame and brake gear.
Once I get a place to run them I will replace the plastic trucks that come
with the kit (which are quite poor) with metal Weaver or Atlas O trucks.
The trim on the swifts premium reefer (the silver one on the left)
was originally the same silver as the body. I thought that looked a bit
bland so used modeler's licence and painted the trim black.
Here are a couple of B&O double door boxcars:
Please let me know what you think! If you have any questions just email me.