Research and consultation continued. Compared thread sealants; ordered Loctite 547 pipe thread sealant for its superior pressure retention properties. Conferred with machinists at St. Pierre Inc. regarding modifying 1/8" NPT tap or using modified plugs as thread chasers. Purchased galvanized steel plugs. Checked NPT thread gauge: 27 tpi. Checked clearance in gear pocket: 1.5". Checked depth of tightened galvanized plug in tapped hole: 1/8". Checked max depth of tapped fitting hole: 1-5/16".