I also said I had ordered the correct replacements from RSLaser Kits, and they arrived
The parts basically fell off the "sprue" and didn't require much manipulation whatsoever to install. There was only a single cut-out that needed adjusting to match the brake wheel mount on the flat car.
The directions were pretty straight forward; however, I would caution that you don't follow their recommendation to start at the B end of the car.
While test fitting the parts, I found that in order to get everything looking symmetrical, starting with the center piece of decking was the best choice. After that the other pieces pair up on either end and the whole install took me about half an hour to do my 4 cars.
I have one more yet to do, but it's in BN "cascade green" - which Wikipedia says didn't exist until 1970. So I'll have to paint and decal this last car for CNR - whenever I stop working 6 & 7 days a week. Right now I just can't find the time.