YouTube - Barbell Hip Thrust great for the posterior chain, i found out about them on T-nation.com and tried them today, I got some funny looks but they felt great.
They work your glutes and the upper hammies pretty good. i don't do them with a barbell, instead i go 20 reps with 5 second pause at the top then unilaterally (i.e. 1 leg at a time) with my feet and upper back both on the ground. they work well to address any imbalances or weaknesses you may have and to bring up the glutes if they are a weak link in your posterior chain. i seriously doubt you'll be able to start with 405. i'd start with what i'm doing and work your way up to the weight.