You know , the early 2000's #38025 and 38044.
In the quest to find an excuse for the extra long firebox.
I'm sure many specific details would be wrong, but could this "abomination" be the approximation of the K5?
I've searched high and low for measurements with no luck. One post from another forum claims the Pennsy used an M1 boiler for the k5. In which case, it appears Lionel did the same for these tmcc k4s.
Pennsy experts please set me straight. I apologize for any anxiety I may have caused😉