Will a low differential ball get me back left (left handed bowler)? I have been throwing higher differential ball with strong covers to get inside. I want to move back left and bowl like a lefty, well a old school lefty. Any thoughts?

Short answer is yes to the original question.  However remember that cover is still 80 percent of reaction.  Low diff with a strong shell can give you the worst of both worlds if you are trying to stay outside.  Balls like Arson low flare and IQ solid are great low diff balls, but you still need some oil to stay outside with them.  Best ball for me to stay out is the Ride.  High rg, low diff, with a tame shell.  I like putting an axis hole on high rg balls because it really smooth the reaction out.  I shot 880 for 4 with a pin down Ride playing 4-5 board on the Cheetah last night.  My IQ tour was just a bit strong for this pattern.  A young guy with a lot of hand shot 890 using a Polar Ice, using speed and loft to stay very direct in the same area I was playing.   

Ride is very condition specific for me too. I use it like a urethane and never go away from the pocket with it. Instead for would go stronger and move in

I'm a big fan of the Radical Rack Attack Solid. I have always been a lefty with an identity crisis. I'm always using strong equipment and hooking it like my right handed counterparts. I just added the Rack Attack Solid to my bag a few weeks ago and absolutely love that I caN square up, close my angles, and keep the shot in front of me. Very adjustable surface, I have mine 500/2000. It works great on our 43ft house shot. As the night goes on, I can make a 4-2 or 5-2 adjustment and get around it a little and keep striking. This ball gets over shadowed by the Guru hook monsters, but it's a tried and proven piece.