Most of the differences between the 216, early 235 and late 235 distributor caps and gears and camshafts are summarized in the master parts catalog. Note that in 1953 and 1954 there are various combinations of camshaft materials and bearing sizes. Here are two pages from the May 1955 HRM article about 261 that give some addotional information about the cams and gears.
Page 5, last paragraph;
Page 6

Hope that this helps your project.

Hoyt