Drills for over the top and lower body rotation

After years of "on again, off again" golf, I'm renewing my committment to improve my game. I'm a high handicapper who has never developed a consistent, confident swing. I'm sure there are many problems, but through video analysis of myself I think I've identified the major problems: coming "over the top" on the downswing and not rotating my lower body to generate leverage/power. This is producing weak and inconsistent iron shots. I'm a big guy (6'3'' around 205 lbs.) but I don't hit the ball nearly as far as I think I should.

Can anyone recommend some good drills to help promote the correct move from the top of the backswing into the proper downswing and on through the ball? As I said, currently I'm getting no power from my lower body and seem to be coming over the top with my clubhead.

By the way, I'm a lefty but I'm used to reversing right and left on any instructions.

Thanks!

Well I'm not sure what others do, but I can certainly tell you what I do ... and I reckon others will use similar methods.

1) Momentus Swing Trainer or similar weighted club. Swinging with one of these promotes lower body action. If you swing with the arms you'll soon know about it, you'll get tired very quickly. It's also very dificult not to use the body when swinging with a weighted club ... or at least I find it difficult.

2) Practice with a friend. Swing to the top and stop. Have your friend grab the clubhead firmly to stop it from moving. Turn the body slowly back through towards and left of the target. If done correctly you should feel your right shoulder drop way down and round. This feeling should help you feel the swing path more easily.

3) lots of amatuerers swing with the arms instead of the legs and torso. Swinging with the arms can cause them to tense and this usualy results in the right arm straightening much too early in the throughswing - generally the very first movement and results inan out-to-in swing from the very start of the throughswing.

TIP: Swing to the top and stop, notice the space between your right hand and your right shoulder (maybe 6 inches? though this will probably be different from person to person) Whatever, try and hold that distance for as long as possibly in the throughswing. This will also help you maintain swing path and promote the feeling of the right shoulder dropping as mentioned in point 2 above. Don't worry, your arm will automatically sort itself out at impact.

http://members.shaw.ca/gord962/drills/top_position.htm
This will give you some check positions to work with...