Effect of raising rear of car?

Thanks this all makes a lot of sense guys and it was mostly what I was thinking anyways, I can clearly visualize how having the rear lower and front higher would transfer weight onto the back on launch. My own '70 Duster sits at about factory height but the springs are pretty worn, I want to get new ones and bump it up an inch over or so but I also plan to add 275/60R15 tires at the same time...

dmsbroker are you saying that just from adding Cal-Tracs your rear ride height went down? How does it make that happen?

Also about the aerodynamics part I got it from a documentary on NASCAR in the '50s-70s, it said how racers found that raising the rear slightly so the angle was just a few degrees up (nothing drastic or even very noticeable) made the car much more stable at high speeds...