I have been using Bavarian Motors in Markham. (on Woodbine & John). The owner is Steve Gaitlits. If you go there, tell him
that Jim (Verona 73 tii) sent you. Steve is an ace with M3-E30 engine. I've know him for >15 years. Over the years, he's done lots of stuff for me (sometimes free) and open with advice (ie not trying to pry the last $$ from my wallet).
He also shares the shop with Raven...folks here love John D (or hate him)....
Steve or John can build you a 2.5L stroker...but they are not cheap.
Another guy that does excellent work is Marcus Glarner in Port Perry. He is one of the few people left that can rebuild the M1 engines. Folks from all over US, bring their cars to him.
Unfornturnately, he is a one-man shop at the waiting list is very long. 905-985-6556. My tii is there right now, awaiting for him to dial-in the kugelfisher fuel-injection.
The last one to try is Autotrend.
I have not gone to him yet, but others have. Don supposedly does excellent work (more affordable too).