Replacing trucks on Trix HO freight cars

I recently bought a set of HO Trix boxcards (UP) because they are so nicely made. The one problem I have is that the trucks are older (journal box) style and I prefer to run more modern stuff. Does anyone know a quality replacement roller-bearing style trucks that will fit the Trix cars?

Are there other appropriate (easy) mods to make the cars a little more current?