Gord, the picture you cite is inconclusive. In fact, the whole book is. Nowhere in it have I found a closed driveshaft. Check sect.0, sheet 15.05, showing exposed U-joints at the rear on a 3100.

Also:

ref. sect.4 sheet 1.00, dated 6-26-53. REAR END SUSPENSION INSTRUCTION, MODELS 3100: The illustration clearly shows an open driveline rear end housing.

ref. sect.4 sheet 2.00, dated 6-26-53. PROPELLER SHAFT & UNIVERSAL JOINT INSTRUCTION, MODELS 3100: The illustration clearly shows an open driveline propeller shaft.

I believe that all '54s were designed to have an open driveline but for whatever unknown reason it didn't turn out that way.

That high serial number is obviously toward the end of the '54 run. It's possible some were built with the open driveline prior to the switch to 55 serial numbers.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.