I understand. I have family in California. for how clean the car is If not keeping it stock i would probably get a nice Ls3 and 4l60 trans kit and drop that in. Literally connect and cruise. I will say one thing with that. If you have the 7.5 rear end I would upgrade to a Grand National rear or a Ford 9 or 12 bolt GM. I went through 3 7.5 rears on my wagon once I swapped to a 450hp 383 chevy. Eventually just installed a Ford 9 rear from quick performance. I would definitely keep the clean buick wagon look 😎
My plan is to keep the external appearance as close to stock as possible. I want to do some 17" wheels and 245 tires, and some suspension. If I do a conventional engine, it's probably going to be an LS3 E-Rod and 4L65. Assuming the price comes down on doing the conversion, I've also thought about doing an EV conversion with a Model S P85 motor in the back. Well-done EV restomods are still crazy expensive right now.