I was searching the subject with Google and one message board discussion I read led me to look at my
copy of "The Diesel Spotters Update" (Pinkepank, Marre, Kalmbch Books 1979 ) in which there is a chapter
on Railroad shops capital rebuild programs- pages 106 to 125 devoted to EMD roadswitchers rebuilt by MILW,
ICG, SP, BN, ATSF, CNW and CR. A common theme is the liberated exhaust system and a central air system,
apparently initiated by MP and omitted from the tally because MP rebuilt it's units on a one-by-one basis as
part of routine maintenance and not part of a program and each unit was a little different from the others.
MILW and BN should be excluded from this group because they installed 645E engines. The only other mention
of 645 parts was that ATSF experimented with 645 parts on CF7 2542 but wasn't convinced to expand the mod
to the rest of the program; the ATSF, SP, CNW and CR retained the original hp ratings. ICG rebuilt 123 GP8's
and 343 GP10's with the frames and blocks being freely interchanged in the process including a 567D block
from a wrecked GTW GP18 and briefly experimented with a 2000 hp rating but converted all back to the
lower ratings after Feb 1969. Interesting subject- there has probably been a more involved article written on
it somewhere and I seem to remember one on VMV somewhere....