Many moons ago I bought a manual gear lever assembly out of a 3500S,If the spherical bush is the same on the automatic 3500 and the 4 speed manual 'S', then I must have a spare roll pin in that 2nd hand manual gear lever assembly, right!?
The pin is the same part number for the 3500S, and both the early, and late, auto gearlever assemblies, so your plan is on the money, providing you can find the 3500S gearlever of course.....