#'s matching car? I'd keep it that way and repair what you have.
how much wrenching re: possible engine removal and re-install would you be doing? Or would you rather have a turn-key service where you drop off the car, the shop does the tear down / inspection / confirmation; a machine shop does what ever, if needed be done; the shop puts it back together and you receive the car fully repaired and functional.
In your other thread re: summit breather tank, you noted this turbo Buick stuff is new to you...
for mechanical shops, I'll mention these...others will add more ideas...
Bruce at Aggressive Performance in MI. link => Aggressive Performance Buick Grand National Parts & Service
Brian Lorenz is in eastern OH. link => Lorenz Racing & Performance
Weber family @ Weber Automotive in N. Olmstead, OH. link => Custom Engine Building and Rebuilding