Stovebold,
If you have the Canadian Pontiac engine with hydraulic lifters, it supposedly had the by-pass oil filter for all years.
"Jim Carter: During the 1955-62 Canadian Pontiac application the lifters were the hydraulic type, the cam gear was fiber not aluminum, and it did not have the full flow oil filter. These Canadian made 261's did not add the full flow filter in 1958 as in the U.S."
The 261 engine was used in some Canadian trucks but I do not know (1) if it was used between 1958-1962, and (2) if it was available between '58-'62, if it had full-flow oil filtration (as the USA 261 had). Also, all truck 261s had mechanical/solid lifters and an aluminum cam gear.
Tim
