OP,
If you notice-
There is a center punch mark in the underside of the receiver at each pin location, opposite side of the bolt stop.
The center punch mark allows a slight press fit to hold the .125"/1/8" trigger pins in place.
Once the receiver is placed in the stock the inlet won't allow the pins to walk out of the receiver.
Oil hardened/annealed 1/8" drill rod pins will last a lifetime.
Oxide coated drill shanks will guard against corrosion.
Dowel pins are too hard for the application.
Roll/spring pins are a definite No Go.
Trigger install referencing a RH receiver-
Pins install from LH to RH side
Insert trigger front into receiver
Align front housing holes w/ receiver holes
Front pin (shorter) of .650" length w/ leade is pushed into receiver to capture trigger.
Seat front pin just below flush (.030"-.040")in receiver as not to bind bolt stop w/ a 3/32" punch.
Insert bolt stop into receiver.
A hemostat to hold the bolt stop torsion spring works wonders.
Insert the rear (longer) .800" length w/ leade pin into bolt stop & catch torsion spring,push pin into receiver.
Swing the trigger group up into position & push rear pin through to capture it.
Seat the rear pin proud on the bolt stop side (.040"-.050" proud)w/ a 3/32" punch.
Installation time is approximately 90 seconds.
2 each 1/8" pins should not be construed as Rocket Science !!