Reply to "O scale PRR mikado"

In general, yes.  There were a few exceptions like the ex-N&W Y-3's that got keystones.

For the L1s above, the round plate is correct except that the background should be black instead of red.  It's easy to change. 

1) Paint the plate, numbers and all, with gloss black paint.

2) Lightly sand the numbers and the raised ring around the plate with #400 emery paper.  A few light swipes is all it takes.