My 3 year old son received a Lionel Polar Express O Scale train set for Christmas from his uncle.  He really wants a caboose.  I am new to O scale. I've been a long time HO modeler.   My question is do I need to replace the trucks on an Atlas O NW Caboose (3Rail standard Cupola Caboose Item# 3003603-2/NS).     Or can I simply replace the couplers on the caboose?   Thought I'd try here as I see Atlas shut down there forums few years back.

Can anyone counsel me on which way to go?

Thank you.

I thought that the case also.  However comparing them side by side they do not appear the same.  The Polar Express couplers seem a little bit taller by a mm or two.   Also, I failed to mention the caboose I purchased will not stay coupled to the other cars with the Lionel couplers.    I thought they would work no problem.  But I haven't really determined the root cause as to why the caboose is coming uncoupled.

Thanks!