brownells sells the standard connector lock pin, which is "GI" length , that's the one you need
they also sell and "NM" length connector lock pin, this is the same length as chinese pin.
Sage stocks are quite easy to install at home.
you will need the following tools
allen keys
castlenut pliers
pin punches
parts needed
usgi length connector pin
1/8x3/4 roll pin for oprod guide
first remove castlenut keeper with allen key
undo castlenut and remove flash hider assembly
undo and remove entire gas assembly , set the gas band plate aside as it will not be needed
using a 1/8 punch , drive out oprod guide pin and remove oprod guide from barrel, set aside as these parts will not be needed
with your sage kit, you will find an oprod guide with holes on the sides that mate to the stock walls. These holes are off center slightly so the oprod guide must go on the barrel the right way so the holes in the guide align with the mounting holes in the stock walls
install oprod guide roll pin 1/8x3/4, loctite optional
in your sage kit will be a small washer that replaces the gas band plate from the gas assembly.
install the washer, then the cylinder to the barrel, ensure oprod guide and gas cylinder are aligned together by inserting oprod to the action and piston in the cylinder. the piston and oprod should be in relatively center to center alignment.
once verified, remove piston and oprod
now, with gas lock installed, check gas port alignment by inserting a 1/16 drill rod or similar "tool" into the small hole on bottom of gas cylinder up into the barrel
the drill rod should pass into the barrel, if it doesn't, the washer may need to be either shimmed or have material stoned off to make it thinner. in my experience, these modifications have not been very necessary to the washer as most are pretty bang on.
at this point you are ready to install action to chassis.
when i do this step, i drop action straight in
install oprod guide mounting screws but i do not tighten them
insert and lock in trigger group
fully tighten oprod guide mounting bolts..... i do not use any lock tite except for the oprod guide roll pin and even then..... not necessary on the sage.
check in stock safety checks and go have some fun
sage stocks are very simple to install and rarely present problems when fitted to chinese actions.