Au irs lsd rebuild/upgrade

[Ben]

Looking at getting my manual AU2 XR8 IRS Diff rebuilt with 3.91 gears.

Understand I will need to correct the speedo with a electronic corrector looking the most likely. Is this best picked up from behind the dash then I could mount the corrector up in the drivers fuse box access panel so I can access it if needed?

Onto the gears looking at the dana spicer 3.91 and get the shop to shim to fit.

Is there anything else I should be looking at for the diff while they are doing it or just a rebuild with the new gears?

End goals for the car are around 350rwhp.