I decided to go with the "OEM swapable parts" route and put a Q45 VLSD into my S13 pumpkin. Let me tell you, it is not a simple ring swap.
1. The Q45 ring gear is thicker, so when you bolt the R200 ring gear to the Q45 vlsd, the diff needs re-shimming to have proper engagment.
2. The Q45 diff uses smaller hardware to bolt the ring gear on, so you need expensive Nismo S15 bolts to bolt the ring gear on properly. I re-used the S13 hardware because I decided IDGAF and I'm going to change to the Villians stubs and a proper diff eventually.
3. The Q45 stubshafts don't fit correctly after that. The long shaft doesn't seat all the way into the diff, and needs to be machined so it sits at an acceptable level. I machined .25" down to the shaft OD, and the metal shield just covers the axle seal. Hopefully this works, but I'd recommend doing .5". I'm going to measure freeplay after I install the axles, and I may or may not have to machine the extra down.
