According to "Ford Illustrated Army Parts Catalog 1940-1942" (S.E.-39-42 Reissued January 1942) the same "Cylinder front brake 1-3/8" diameter" were used on F15, F15A, F30, F60S F60L F60H and GT. This was part number 92Y 2192.
The listing then gives a separate listing for those vehicles using the 6" joint (F60S, F60L and GT) - part number C118Q 2192 - "Cylinder front brake 1.38" diameter". (interesting that they chose to use decimal notation: 1-3/8" is 1.375', rounded to 1.38')
In this publication, "Cylinder rear brake 1-1/2" diameter" 91T 2192 is listed for the same wide range of vehicles F15, F15A, F30, F60S F60L F60H and GT.
I don't have the individual parts listings for F60S or F60H to compare but the F15-01, F15A-01, F60L-01 and FGT-01 lists all match the above.
To compare to Chevrolet practice (who used Ford brake parts on the F15A up):
Parts lists 175 and 197 (wide range lists) only list the wheel cylinders for C8 and C15 (the ones with Chevrolet brakes).
Parts lists C15A-04, C30-03 lists front brake wheel cylinder part 92Y2192 (no size given),
Parts lists C60S-03, CGT-03 list 1-3/8 cylinder 92Y2192 for vehicles with 5" joint, 1-1/2" cylinder 91T2192 for vehicles with 6" joint (serials 184--28127 to 284--00003) and 1-3/8" cylinder C118Q2192 for vehicles with 6" joint (serials from 284--00003)
C60L-03 follows the same sequence but doesn't give the serial number breakdown.
From the above, it appears most 3 ton (maybe all Ford 3 ton) CMP used 1-3/8" front wheel cylinders.
A theory to explain larger wheel cylinders at the rear compared to the front might be that the trucks were designed for the loaded condition where the rear axle was more heavily loaded than the front so more braking was needed at the rear. The Chevrolet lists suggest there was a plan to standardize on one wheel cylinder for front and rear on the heavier vehicles with 6" joint and that it may have been less than a complete success (I'm guessing) so they reverted to different sizes front and rear.
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