My 1960 and 1959 261s have both holes G. They were not used but they are threaded. I use those holes to hold a full-flow remote, spin-on oil filter head to the block.
I do not understand Racecarl's reference to a by-pass filter being used with a 58-62 block. If you do not use a full-flow system on 58-62 blocks (and never moved the pin/diverter-plug) does a by-pass filter work on the 58-62 blocks?
