you've got the parts you need, the orignal trigger pins also hold a retaining spring for the new fcg, on Sheiks conversion page he used two binding posts to replace the original pins check the bottom of step seven.
i'm in the middle of the pg conversion aswell
i went through k-var for the pg screw and nut and i also got a new trigger gaurd with the mag catch built in. i went with joeken for the the saw fal grip, buttstock and a muzzle brake. and cheaper than dirt for the fcg
-thomas