The N/A Buick V6 is not like the turbo V6. The crank, rods and pistons are different so you'd have to change all that. There is the matter of air & fuel, EFI is best so an 86/87 intercooled GN motor would be the way to go but also most expensive. You could use a hot air engine and add an intercooler, air to air or air to water.
I like the Buick V6 but to make it turbo would cost probably more than it's worth. Not because it's a V6 but because of all the things you need to make it work, computer, wiring harnesses, exhaust, the turbo and long block. I'm not going to try and dissuade you from what you want to do but be prepared to pay more than what you're probably thinking it will cost you.