It would be easier to just replace the wheels with Proto 2000 wheelsets in the existing trucks.
Do you have the ATLAS trucks yet?What I concider the smart thing to do since Bachmann uses screws to mount their trucks is to retain the screws.
In order to do this you will need to ream the center hole out in the ATLAS truck so it will fit over the Bachmann mouinting post then just simply remove the Bachmann truck and replace it with the ATLAS truck and insert and tighten the screw.
On some Bachmann cars you may have to shorten the screwpost to get the truck to snug up.
Easiest way to ream out the hole on the truck is with a fresh #11 blade in your Exacto knife ream a little from one side then flip the truck over and do the other side.Keep doing this till the truck will just slide over the screwpost,if you feel any drag when you swivel the truck do one or two more light passes then check it again.
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I have several Bauchman rolling stock that I would like to change the trucks and couplers to Atlas. Is there a special truck that will work? I do not want to re-invent the wheel to do this, but if I can do it without to much trouble I will. Any suggestions? Thanks. Mike
Edit. This is N scale. Mike