That whole area over there with the Poston set up is a little odd. It is very hard to get a socket over that bottom bolt....
I had studs welded into my headers, and it made it alot easier to get it lined up, and started. The trick with the passenger side is to get it so that both studs/bolts are equally tightened.
Don't put alot of torque on those poston flanges, torque'ing them down tight does nothing to help create a tight seal, but it only distorts the flanges on the crossover pipe(don't ask me how I know).
Getting the correct number of turns on each side is the way to do it, if more pressure is on one side it will tend to let the other side leak....back both bolts out, and give them 5 turns each till their snug....then by feel and alternating get them to full torque which is usually "nice 'n tight".
I hope this helps you.