From what others have said, my own observations since I started driving Chevy sixes in 1953, and the information in the
Resto-pack specifications , I do not believe that filters were ever standard on the passenger cars or trucks with 216s or 235s. Bypass filters were available as an
RPO on the passenger cars and trucks with 235s. It looks as if the full flow filter was standard on 1958 and later trucks with 261s. You could look in the
the other links on this site for more data.
As I look at your dipstick and tube measurements I'm beginning to think that someone has installed the longer tube in your 261 block. This could explain the need for seven quarts of oil. The manual is not clear about the need for a shorter tube for the 55.1 truck engines; however, I thought that they were similar to the 54. I will look at my early and late 261s again tonight (or tomorrow).
Hoyt
