53Therapy,
This reply won't be of much help - more questions than answers.
1. What manual are you using? The 1954 Truck Shop Manual?
2. The 1954 (and maybe other years) rocker arms and shafts for the 261 were supposedly "beefier" than those on the 235 (this is stated in the 1954 Technical Specification Manual). The arms have different numbers on the 261 (1, 2, 5, 6) than on the 235 (9, 0, 3, 4).
3. The 1957 and 1960 Truck Shop Manuals show completely different numbers on the rocker arms. Most likely, the automobile 235 rocker arsm also have different numbers.
4. Nonetheless, most likely, all 1954-1962 235/261 rocker arm assemblies are interchangeable (in other words, they will fit on all the 1954-1962 235 and 261 engines). I would guess that they will all work OK for use on smaller trucks.
Regardless of the numbers on your arms, your Manual should show the orientation (and shape) of the rocker arms ("Fig. 15 - Layout of Rocker Arm and Shaft Parts" in my 1954 Manual). Also, the Manual shows the differences in body profiles for the Inlet and Exhaust arms (Fig. 14). Let me know if you want pictures posted (I could post them tomorrow).
Good luck,
Tim
