Hi Brad. I thought I'd give you a bit of info on what I've found out about the Buick V6. From what you have said it's hard to tell what model/year/type the V6 is that you are talking about. I did alot of research/time into the v6 motors before purchasing one. I purchased a 20'000 km, 3.8L( which is the same as Commodore) supercharged Buick v6 97 model(vs-vt eqivalent).From what I found out was that these american motors are set up as front wheel drives, so therefore there are alot of things on motor that need changing for it to fit into FC or any other rear wheel drive car.(can give you more exact details if required) You can then buy from Holden or V6 conversions the necessary parts to turn this Buick motor into a Commodore spec motor,( around $1800) which is what Holden do before fitting them to their commodores.
I was set on a S/C v6 & looked around for months for a wrecked S/charged commodore but with no luck. This would have been a much easier/cheaper option but as said I had to go the other option.
With this said the V6 Buick motor you have could have also been set-up for front wheel drive as mine was.Let us know.
Hope this helps in some way. Good Luck
Harko- Are you sure your mate has a s/charged vn-vr motor. If it is it must have an aftermarket s/charger set-up, because as far as I'm aware the factory blown motors didn't come out till VS model. That's some awesome power 225 KW more than the eqivalent V8
Miikael