Alright, so here's the scoop. I got sick of waiting a week+ in between emails with Spence at Weir Performance, so I went about finding an alternative gear solution. Based on some stuff I was reading, I decided to buy a set of Motive Gears for a V6 toyota (People were saying that pretty much any 8" ring/pinion for a toyota would fit). I went with the V6 over the 4 cylinder version because it had the correct tap size for the ring gear attachment bolts. Here is the link if anyone else wants to go that route.:
http://www.jawsgear.com/Ring_And_Pin...s-Toyota-8-V6/
That being said, after a quick comparison, it is quite clear that the Weir Performance pinion gear has MUCH thicker teeth than the Motive Gears. Probably on the order of 20%+ if I had to put a number to it. So if you want to go higher power than stock, I think that is probably the safest route. For a stock-ish FRS, I'm guessing the motive gears will work just fine.
I put the OEM differential back in yesterday so I could choose not to rush this rebuild (the car feels hella slow now). I bought a 12 ton press from harbor freight, which made the process go so much faster. If you don't want to buy a press, there is a trick for quick setup. What you do is you take an old/scrap pinion bearing and sand down the ID so it can be easier to put on/take off. Use this bearing for setup and then once setup is done, use the new bearing to get final position and for install.
Here is the progression of pattern I saw as I went through setting up the gears. Measured the backlash to be .011 (.007-.009 being preferred), so I will be buying new shims along with new seals (noticed some diff oil on the under side of the car upon removing the 4.56 diff last).
First Setup:
Second Setup:
Final Setup:
(180deg from first image)
After correcting backlash, I'll recheck mesh again before install. Relatively happy with where it sits right now.