early lionel scale k 4

 The biggest "flaw" is the overly long firebox, that is not accurate to the prototype. I believe its 1" to 1&1/2" too long.

Here are photos comparing the older TMCC version to the legacy version. Even though the photos are taken at different distances, the firebox difference is still very obvious.

Tmcc k4

Legacy k4 ( k line tooling)

There are plenty of Pennsy experts that may chime in on any other details.

Heres video(not mine) of the TMCC version if you haven't seen it in action. FWIW the 2 chuffs per driver revolution is prototypically incorrect also, it should be four.

The second issue with that model was the squashed trailing truck found under to over-sized boiler. It appears to make the trailing truck work, Lionel stuck under the boiler the 2-8-2 trailing truck. This makes the model stick out like a sore thumb. I sold mine and replaced it with the k-line versions ad well as the Williams brass brsion. The current legacy version is where you should spend your $$ on. To correct that trailing truck with a correct scale one is difficult at best and will limit the loco to only super wide track radii.

LKonel on top- K-line in middle 

K-line

Lionel

Lionel and correct brass trailing truck for reference

There were two cab numbers. 1361 had historical significance related to Horseshoe Curve/Altoona, PA.  I believe one of the first Odyssey offerings.

I agree with all of the posts on this loco. I am a stickler for accurate proportions so when I had a chance to pick up a K-line version I bought it and gave the Lionel loco to one of my brothers who happens to work for the UP in Chicago.  Aside from the accuracy of the proportions it was a good smooth runner for me.  I have just recently modified the K-Line K4 to 4 chuffs and I am happy I got it.  But if I knew Lionel was going to come out with the new accurate version, I would have bought the Legacy version for value and features.