If you are looking to shoot heaver bullets out of the rig, then an Garand adjustable gas plug is all that is needed.  There are two type out, once with a set screw that is spun out to increase bleed off, and the other with  fixed screw in orifice bleed off bolt type valves that are change out out to the needed side instead.  Of the two, I prefer the later, since it faster to just back and forth between port bleed off setting, such as if you are shooting 110g bullet at reduced range matches, then drop back in the larger bleed off port for 168gr rounds.  And yes, it will even come with a port if you want to load 220grs as well.


This is the one I prefer,
http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/gas-system-tools/m1-garand-adjustable-gas-system-prod1538.aspx

The set screw type instead, and a pain if you are adjusting it for different loads.
http://www.brownells.com/rifle-parts/gas-system-parts/gas-system-kits/adjustable-gas-system-prod20456.aspx