Are you referring to 3 rail trains?
If so, I don't think you can buy the upgrades.
The importer/manufacturers want you to purchase a new train, not just some parts.
Of course, I could be mistaken...........
Which brings up a good point in "O" Scale, how little or few upgrades are available in our hobby compared to other and different hobbies. Oh sure, there are a few, but with all the skills I see posted here on the Forum on scratchbuilt items, surprised someone has not jumped into making these available so upgrades can be made to items without paying and waiting for a "Vision Line" to appear.
I'm sure a steam whistle/blowdown chest steam, etc. can be made without having to wait/purchase a Vision.
Amazing how much is available in other scales at reasonable prices. When I was in "N" and "HO" I found and was able to upgrade every engine to sound and those I wanted to, smoke, and remote control systems without having to buy new.
