The Lionel L1 #490 uses what was in the 90's a "standard" Lionel Hudson frame which is based on a NYC J1 Hudson. The actual 490 has 74" drivers whereas the J1has 79" drivers. The overall length of just the engine of the L1 is shorter than the J1. Because of the compromises Lionel took with using their existing Hudson frame, the 490 is not quite scale. However, until 3RD Rail produces their version of the L1(hopefully around the end of the year) the Lionel version is the about as "scale" as you can get.
Ken