Torquing the Flex Plate

1972 Duster with a 1967 225 and a 1974 904 automatic.

After 300 miles of local running on the newly rebuilt engine and trans, I took the car on a 400-mile inaugural long-distance run. 300 miles in, two of the flex plate bolts loosened up, sounding like a fork in a garbage disposal. Easy enough to fix in a Washington DC parking garage, but I noticed that I can't fit a socket wrench or a torque wrench in the small space between the oil pan and the flex plate to properly torque the bolts. What have you guys used to torque these bolts? I can use the "calibrated arm" and an open-end wrench, but was wondering if there was something a little more technically correct. Also, do you use loctite? Which color?

Before you ask, I know it's not a crank pilot hole issue between the early engine and the late transmission. I special-ordered a modified torque convertor from Hughes that had the small snout (to mate with the early engine) but the right spline count to mate with the late transmission.