Later model 261's had the option of running a full flow filter, but I don't think that was available in 1958. Those engines will have two large pipe plugs (1/2" NPT) on the driver's side near the exhaust pipe, and a round dowel pin that must be driven into the block about 1/2" to change the oil flow from the pump to the bearings. When that is done, all the oil from the pump passes through large-diameter flex lines after it leaves the pump, goes through a tall, large filter canister, and then re-enters the engine to provide lubrication. That's the system Dragsix was referring to when he mentioned leaks. A bypass filter line can also spring a disastrous leak and pump the engine dry or start a fire, so be sure the flex lines are in good condition. Some people choose to plumb the filter with hard line tubing and add a "vibration loop" to the plumbing to prevent the lines from stress-cracking. That's OK as long as the filter housing is on the engine somewhere like the intake manifold, not mounted over on a fender well, etc.
Since oil filters were often dealer-instaslled options, using flex lines to connect them made more sense than hving hard lines made up to fit a lot of different filter mounting locations.
Jerry
