As a GP35, the 216 has a turbo, which the 252, as a GP38 does not. Some
shortlines, such as the Vermont Railway, have sold off some GP40s and added
GP38s to their roster, as turbos are supposedly expensive to maintain and
replace. However, I seem to remember some comments in the past, that
the turbo on the 216 does not cut in much, with the leisurely pace of the
CSRR trains. The 216 does have a high short nose, versus a low nose on the
252, but that would not seem to be a major factor, as both the 573 and 1751
have high short hoods. If, in fact, the CSRR wants another 38 to replace the
216, maybe it is not "playing well" with the 252.
I am not sure there is much of market for a GP35, whereas a well maintained
GP38 will cost big bucks,