Essentially anything that is MTH RK (not RK Scale) or Lionel Traditional (and the K-line/WBB equivalents) will be in size sync with the 1:58 K-Line 2-6-6-6 (or K-Line - now WBB - 1:58 4-6-2). Think Postwar (not the really small stuff) dimensions.
I have one of these. TMCC. Cruise. Runs very well. Except for the "high-pockets" firebox sides for rear swing on tight curves), it's a pretty fair model, and correctly proportioned. Great free-lancing fodder, also (I haven't done this).
I may modify those firebox sides one day (if ever...) as I have 072 curves so clearances aren't critical on this loco.