Hi Cody,
If you are looking for a simple "bolt in bolt out" solution, I may be able to help via trade. I'm swapping my auto RS4V from stock subframe to a reinforced S14 Rear subframe specifically for track duty. I was looking into different rear core options while the car was in air and I found your thread.
My VLSD rear is freshly changed fluid/inspected. I will say even with Redline diff fluid it is still not as aggressive as I would like with the "sports" viscous core, and coming from a heavily modded evo with full drivetrain I'm looking for a bit more rotation with the throttle.
I second this, the polyurethane bushings are pretty aggressive as is.
If you're interested in the trade, I am driving out to Chicago in September for a time attack event. I could swing by and make the trade somewhere Sept 12-13th or 15-16th if you are interested and you have not already solved this issue yourself.