My mechanic that me and my family have been using for over 15 years is in Markham (HWY 7/McCowan area).
He doesn't specialize in 370z/isn't a tuner shop - just a regular mechanic but it's honest work and he charges very fair prices (cash pricing
). He's a small shop. Does a great job at giving you a few pricing options depending on what parts you want to use (OEM/Aftermarket brands). I'm sure he can do a diff bushing.
There are some tuner shops next to his if that's more your thing - but I haven't worked with them before. They seem to be always busy.
PM me if that area works for you.