@Donnie Kennedy- beautiful engine and yes the scale Hudsons are big. If you are not too concerned about collectability, the "scale" size Harriman cars should be reasonably available MTH and Williams for example both made sets of larger versions than the Lionel cars in the 1980's and 1990's. I have a set of Williams SP Daylight cars I use with my GS-4 and it looks good.
Best Wishes
Don