Rebuild or New

The nine inch will be more costly but has the advantage of being able to swap gears in half an hour for when you go to the drags

... Plus, you wasted all that money on the rebuild, you could have invested in the hardware you might probably resell once you rotate the race stock or what have you. I would not sent that money toward a rebuild when the 9 inch is penny wise is you are going to get it up the rear end no matter what gear oil you use is start with some fresh new parts back there is your worry about the rear end is over.