Well, as you may already know, Walthers 89' flats are going for about $25, which IMHO, is a great looking & running car; and Atlas' 89' pig is due to be released soon also. Now as for Con-Cor I can't speak for the flats, but I can certainly speak on their spines.
Long ago, my brother & I jointly bought a Con-Cor 10-car fuel-foiler spine kit. To date, I think it was the worst thing we ever did
. It was weighted all wrong, with the weights located inside the spines instead of over the wheels, you couldn't run it midtrain and certainly NOT up front; it would have to be THEE VERY LAST car on the train (and if you run cabooses, it would need to be behind that too! *sighz*). Not only that (as if that's not bad enough), it wouldn't hold or balance for long any trailers other than Con-Cor's (most of which were totally unprototypical), and I still shudder to this day when I think of the nice, long, accordian it would make whenever we EVER decided to back up with it!!!
To be honest, I really hate to slam on a product like that; but OMG what a piece of crap!! *sighz*
. Needless to say that it was the 1st and last Con-Cor car we ever invested in.