Sorry for not replying sooner, Dave, but I just happened to stumble upon your thread now.
(The stumbling bit seems to be getting more frequent, too, since my wife swears that she didn't push me down the basement steps)
I make the roofwalks from Evergreen HO scale 2"x6", although .020"x.060" strips are useable, too. Before cutting them to the various lengths needed, I drag a razor saw down their lengths, both sides, then determine what lengths are needed for the car on which I'm working - I like to make the end pieces longer than necessary, then trim them back after they're in place on the car. Cut the pieces to length, then toss them in a pile -when you pick them out at random, there's less chance of the "grain" matching that of the next board. If necessary, flip the board over or end-for-end, as too many matching end-grains look almost as if you used single full-length pieces.
If you need roofwalk "saddles", use strip material of a greater vertical dimension than that of the car's roof ribs, unless you're mounting the saddles atop the ribs. In the photo below, the car on the left has short pieces of such strip material cemented to each side of the roof's peak - note that the outboard ends of the strips are at least as high as the roof battens are where they meet at the peak.
Once the cement has fully hardened, flip the car onto its roof and carefully rub it end-to-end over a sheet of sandpaper secured to your work surface, keeping the car's sides perpendicular to the paper. The car on the right has been thus sanded, with the saddles now about level with the highest point of the roof battens.
I add support strips for the roofwalk laterals using material similar in thickness to that of the battens, but you can use thicker or thinner material to suit the height of the roofwalk.
Here's a different car showing the overly-long roofwalk boards and a lateral under construction:
Most of my re-built cars use Tichy ends, but if I'm building a car which requires end sills, I usually use Evergreen channel. On the car below, it's .080", but I try to suit the size to the particular car. Your Van Dorn end looks like it has channel-type end sills, but they seem to be a little higher than those on the Pennsy car.
The Van Dorn end was introduced in 1909, and was supposedly the first all-steel end, pre-dating even the Murphy. Besides its unusual appearance, it's unique for being a one-piece stamping. The first Murphy ends were three-piece stampings (later two-piece) and the Hutchins ends two pieces.
The Van Dorn photo which I have is of an Espee boxcar, and its end sill appears to be a channel-section, but with the open face towards the car. In addition, it's thicker (front-to-back) at the coupler area, and tapers somewhat towards its ends (somewhat like the blunted prow of a ship).
Another photo in the same magazine article shows a gondola with what may be a Van Dorn end, although the rings are in a spiral shape rather than concentric.
For corner steps, I use the ones from
A-Line. They come in three different styles and are formed from phosphor bronze, so they stand up well to handling or in-service. Simply drill the bottom edge of the car's sides, press them into place and apply a minute amount of ca. If the car's sills are too narrow (as shown on the car below) add a filler piece and allow the cement to fully cure before drilling.
Wayne