Sounds like the pressure spring is there. It is not a contact spring.
All you need are:
shoe
backing plate
rivet
First remove the collector assembly from the truck (2 screws).
Keep track of the insulation and spacers.
You have to slip the backing plate under the pressure spring.
Put in the shoe/rivet from the outside and clinch.
Solder a lead to the rivet.
These are the same parts that are used on an operating car pickup, and go together the same way.
Make certain you have the shoe orientation correct.
Got it! Now for the challenge of the riveting once again Gigantic press ready to crush the life out of a wee rivet ....
BTW, slight topic diversion, that was the neatest motor I have seen from Lionel so far - top and bottom thrust bearings, really cool. And (screw) removable side frames - yay! And it runs smooth after enough hours of play time to wear grooves in the collector rollers!
Flat side of the shoe to the outside, is what I read......