"The M-26 had the early ARA underframe with 5 foot from bolster kingpin to striker distance (most freight cars use 5 foot 6 inch) which places the wheels closer to the end of the car."
Actually, it's the other way around. Class X29 had the 5 ft spacing, while most of the ARA cars had the 5 ft 6 in spacing.
If length over strikers in 42 ft 3 in, distance between kingpins is 32 ft 3 in, kingpin to striker distance is
(42 ft 3 in - 32 ft 3 in)/2 = 5 ft
"All of the B&O M-26 variations except for the M-26b used the 1923 ARA body rivet pattern."
This is true. The M-26b was a direct copy of Class X29 down to the ladder/lower grab arrangement to the right of the car side and kingpin to bolster spacing.
One other note - the photo dramatically shows the main spotting feature of the Duryea cushion underframe - the centersills and brake system components, which pop out on the wintery background. (Everyone brings up the extended couple pockets, but that detail's more difficult to see compared to the "extra" stuff hanging below the car.)
