Sounds like a "built up" set.  The 2026 can be a 2-6-2 or 2-6-4.  It never had a 4 wheel pilot truck from the factory, nor will one fit.  Good solid entry level engine.   There are online guides to what made up each set and from what year.  I used to have the book but loaned it out and it hasn't returned yet.  Unless the set comes from the original owner, then I look at it as possible assembled from seperate items to make up a set that once exhisted.  Replacment part alone are not proof of this.  These were toys, parts got broken or lost over the past 50+years.  As long as it runs good, that was a fair price for all of that.    Mike