Looks like they have all come in and sold out already at one shop north of Baltimore that this site blocks the name of. These are a re-run of a Centerbeam Atlas offered years ago in two runs and aborted the 3rd run. They finally reran them recently. They are way to modern for me but look very nice and detailed. If you are interested, don't wait as they are selling out fast. Same goes for the Atlas HO FMC 5503 double door box cars released about the same time - the SP are pretty much sold out everywhere already.
I am a big fan of all the master line cars. If you can find one for a decent price, it would be a great car to have for a modern layout. I was looking at some on eBay a while ago; people are selling them for some big bucks. I don't have any, but they look to be more detailed than the Walthers ones.
If you are modeling the last 25 years appox, then the Atlas Centerbeams are up your alley. But they were only released about a month ago and are getting hard to find already.
I just picked 9 that I had pre-ordered, WOW, they are probably the nicest cars I have on the layout! Great detail, and they run good too!
There are some possible lumber load you could make from either Wheels of Time: http://www.wheelsotime.com/ho-scale-lumber-load/ They do need to be painted and strapped but I'm guessing they can be fitted onto Centerbeams as well as standard flat cars and bulkhead flat cars. Option two are the very nice Trainlife lumberloads: https://trainlife.com/products/ho-scale-laser-cut-lumber-loads-kits?variant=5136247259165 There are also Grand Central Gems with logo's: http://www.grandcentralgems.com/salt-lake-city-lumber-loads.cfm
Now you will have to build the McKean centerbeam. I've never built one, but I hear they are real "fun."
Been there done that: It was wrongly painted dark blue for WP so I had to air brush it black - here is is (above without decals). I decided to sell it after I got the much nicer ExactRail versions below. Here is the FR version next to an ExactRail version - note the height difference:
