LC 120th Santa Fe set

I am guessing you have Lionel 2022120. This would be a copy of the F3 from the post war period and any Lionel Santa Fe F3 B unit should work. All of the electronics are in the powered A unit and the unpowered A unit. The B unit does not need anything operational. In 2005, Lionel made an ABA unit that had a #19 powered A unit, a #19C unpowered A unit, and an unnumbered dummy B unit. The two A units had smoke and the B unit did not. This B unit was not available separately. So, you need to find one from a set that has been broken up or one from a different year.

That set John mentioned won't work. That was a scale set, not a traditional set like the OP has (apparently). Bob, you need to give the Lionel set number of your train so people can be sure what item you're talking about. John's probably right that it's no. 2022120, which has traditional type F3 engines (Lionel hasn't made any scale LionChief F3s). So Bob has a lot to chose from, given that there are usually plenty of traditional style F3 Santa Fe B units for sale on the Bay. The only question is whether the silver paint will match his engines. The B units won't have the (what looks like) simulated stainless panel on the bottom of the sides (where the Santa Fe lettering is), because this LC set is the first to have that on a traditional F3, but hopefully in other respects the B unit will be a satisfactory match. Lionel no. 18103 and no. 18115 are two commonly found add-on B units you could try.