MELGAR, after seeing and reading/re-reading your post did a little research from Model Railroader Cyclopedia-Volume 2 "Diesel locomotives and "Pennsy Power volume III & II. As stated mine is a MTH RK but was catalog as "Scale." And my loc scales just under 44-feet from front pilot step to rear pilot step (just under 10-1/2-inches.
Just took these two pics. The second one is with loc on top of Pennsy Power III opened to pages on EDD diesels. The image right below my MTH front truck is in fact the SW1 road number 9138 same as the MTH model.