The F7 superseded the F3 in production in 1949 and Santa Fe orders
from that point were delivered as F7's. F7 passenger units continued
their numbers upwards from where the F3's let off. The 37 class
of F7 passenger locomotives was comprised of A-B-B-A sets 37LABC
through 47LABC plus one single B-unit numbered 48A.
They had the same basic appearance as the late 16 class F3's except
the D/B had a circular fan rather than a pair of slits covered with
"chicken wire." In this class the 1949 delivered units 37-41 had
a 36"D/B fan while 1951 delivered units 42-47 and 48A had a 48"D/B
Some of these units were delivered with horizontal-slit grilles,
but all were changed to the vertical-slit type early on. Stewart's
F7A "Phase II" has vertical-slit grilles and a 48"D/B fan but it
is not painted and lettered for Santa Fe. Detail Associates vertical
slit grilles would need to be applied over Stewart"s or Athern's
Santa Fe lettered F7 horizontal slit grilles in order to model units
37-41. A 48" D/B fan from Highliner B-unit kit could be installed
to model units 42-47 and 48A.
The 300 class of F7 passenger locomotives were built concurrently
with the 37 class and they were identical in appearance to the 37
class except they were arranged in A-B-B sets instead of A-B-B-A,
apparently the only reason they were assigned to a separate class.
1949 delivered units 300LAB through 305LAB had 36"D/B fans while
314LAB had 48" D/B fans. All had vertical slit grilles, so the same
modifications mentioned for the 37 class would also apply to modeling
the 300 class.
While in Amtrak service two of the 300 class F7A's (304L and 315L)
and one F7B were repainted into the yellow warbonnet paint scheme,
but Amtrak apparently did not like the yellow scheme and no further
units were repainted while Amtrak was using the 300 class units.
The 325 class passenger F7's came about because the Santa Fe desired
some locomotives geared for dual service, either passenger or freight.
Built with compromise gearing for 80 MPH, the first units of the
class were numbered in with the 300 class as number 306LAB through
316LAB when delivered in May 1950.