(My Krag inexperience is showing here...)

I have learned recently that sporterized Krags have used
either the Redfield or Pacific peep sights that attach to the
LH side of the receiver. Do both of these require the removal
of the cut-off switch? Or is there a peep sight that doesn't?
Is there any on-line reference source to find out more info,
perhaps starting with make/models of the different sights?

Any info you wish to share would be greatly appreciated.
                                                         Thank you!
                                                           -Mark-

Watch Gunbroker and ebay for old Krag aftermarket sights. Expect to pay $80 and up. I have a Redfield no-drill that I found on gunbroker several years ago. It does take a longer magazine sideplate screw. Fortunately, mine came with one. It is a very good target sight. Not sure about the Pacific sight. I believe Redfield bought out Pacific many years back, so the installation may well be the same.

The Redfield and Pacific sights differ from each other.
    Redfield bought or was a name-change for the earlier Western Gun Sight Company, Denver, Colo.  This firm built the #102-K sight which utilized locking screws for windage and elevation settings.  Later, Redfield added the #70K micrometer receiver sight to their line.  All these models were held in place with a longer side-plate screw and a sheet metal plate that hooked into the magazine cut-off opening.  The cut-off removal required no permanent change but did cause a roughness in the magazine feed.  Later instructions suggested cutting the shaft off the cut-off and putting it back in the opening.  The Redfields did not require altering the stock.
  The Pacific sight was made in San Francisco, Cal.  It is quite compact and has a shaft that slides into the (removed) mag. cut-off opening.  It is locked into place with a set-screw that bears against the receiver's cut-off machining.  The Pacific feeds smoothly because it fills the cut-off void.  It may require a slight notch in the stock to allow the lowest settings.  The "basic" Pacific had elevation locked in place with a knurled/coin-slotted lock-screw.  The eye piece can be drifted side-ways and clamped in place with a fine screw.  There are also similar micrometer versions of the Pacific.  Butlersrangers