I have a friend going through his 489 case 8 3/4 axle and he is tossing around the idea of using a full spool instead of a sure grip differential. He asked my advice, but since I have never driven a car with a spool or had any expereince with them, I didnt have any sound advice to give him. What do you guys think? His car is a 1969 road runner with a potent 500 incher and it sees some drag use and street use. Probably a low 11 second car if he could ever hook it up