The front cover of this past May's issue of Trains Mag, has a photo of a Rock Island RR train, in Illinois from 1974, the lead unit being a U-25b class, # 226.
The MEC purchased 14 of these units, #'s 225 to 238, for mainline service, although four were most likely used for parts only. The units were re-painted in MEC colours and retained their Rock Island #'s.
As a matter of fact, unit # 226, was the first to receive the Maine Central paint scheme of the time.