Takes some preparation and favrication of a couple pins. The factory staking was done by using pins with short holes drilled into the ends and the ends flared with a punch after installation. Common technique with wartime German MGs.
Make sure you have all the parts for the sight and the indexing arm which include the body that holds both parts and the springs and the plungers. I will refer to the part that holds both the sight and the arm as the "body".
Prepare two pins that are longer than the distance between the outsides of the two holes in the shroud for holding the sight and arm body. When the pins are put into the mount holes, they should extend about 3/32" to 1/8" past the side of the mount on both sides. Center drill both ends of each pin with a drill that will leave a wall about 1/4 the width of the pin and drill in at least 1/8". Chamfer the ends of each pin very lightly. Test fit both pins and make sure they are an easy fit into the holes in the sight body shroud mount and are extended on eac side the correct length. Better to have them a bit loose fit in the holes to allow for any alignment issues when installing the body.
The way I install these parts is as follows: make a couple slave pins which hold the sight and the arm in place in the body. The slave pins must be only the width of the hinge holes of the sight and arm and cut flush with the outside of each hinge hole. Chamfer the ends of each slave pin slightly. Assemble the springs and plungers and then assemble both the sight and arm into the body with the slave pins. Make sure the slave pin ends are flush with the sides on both sides of the sight and arm. If they stick out on one side or the other the body will not fit into the sight mount rectangular hole of the mount at the muzzle of the shroud. Make sure the sight is assembled in the body with the sight blade in the correct orientation.
Once the body has been assembled with the sight and arm, fit the body into the mount recess in the shroud. Line up the end of the slave pin in the sight mount hole and make sure it is aligned as closely as possible with the hole on the other side.
The next operation is the tricky part! Anchor the shroud in a position that makes driving the pins into the shroud mount easy and with the least amount of awkwardness. Push the long pin into the shroud mount hole of the sight and carefully push it against the slave pin pushing the slave pin in only enough to ensure that the long pin in started into the hole. Using a punch that is SMALLER in OD than the OD of the long pin and preferably with a short center nib in its face that fits into the hole in the end of the long pin to keep it on the end of the pin, strike the punch a sufficiently hard blow to drive the slave pin out of the sight body and out through the shroud hole on the opposite hole with the long pin following so it goes out the hole on the opposite hole but but not out of the hole on the striking side. Even if the pin goes into the moutnt hole too far, backing it up is comparatively easy once the long pin is through the body and out the other side of the shroud mount.
An alternative technique is to prepare a three inch or so pin that is the same OD as the finish long pins. Instead of driving the long pins through the shroud sight mount and pushing the body slave pins through, use the three inch long pin. The extra length allows for hand manipulating the alignment of the body with the shroud mount hole on the other side if it doesn't quite line up when pushed through. Then the extra long pin can be pushed out by the finish long pin, again allowing hand manipulation of the body for alignment of the finish pin as the extra long pin moves out of the body.
Final operation is to flare the holes in the end of the finish pins to keep them in place. Buck the offside when using a centerpunch to flare the ends.
Hope this helps......
You're right, no special tools, but I would suggest a third hand from a buddy, and use loose pins to hold together till you force in the permanent ones.
A HUGE thank to you both! Black Rivier Militaria you make it sound like I can actually do this. I am not very well versed on metal working myself, more of a IT kind of guy but I can fix most things around the house. I will try to do the installation according to your well-described plan. I will post pics if/when I get it done
Thanks again, really appreciate the time you took to type it all out for me.