I think you'll be very pleased with the results of switching to a Turbo V6. We have quite a few ex-camaro, ex-mustang, etc. guys here who are blown away with the capabilities of these little V6's.
The most desireable Turbo V6 is the 1986 & 1987 one. It's the easiest (due to larger aftermarket parts) and most resonsive to modifications. Checkout out the recipes at GNTTYPE.com to get an appreciation for who affordable it is to break into the 12's and 11's. Ideally, you would find a T-Type which is usually cheaper than Grand Nationals even though they have the powertrain. Of course, if you just gotta have that sinister blacked-out look like me, go with the GN.
Actually, B.C. has quite a few local Turbo Regals. Checkout local auto ads, GNTTYPE.com cars for sale, this site's cars for sale, Auto Trader, etc. Also, you could contact some of the locals enthusiasts like Grand National Racing Association
gbuick@rogers.wave.ca and British Columbia GS Specialty Car Club (604) 590 0766.
I had a difficult time finding a nice condition, low mileage GN around the Pacific Northwest, so I almost had one shipped out here from Kirban
http://www.kirbanperformance.com/
I eventually found mine in Victoria B.C.
I don't believe the new 3800 motor has any resemblence to the classic Turbo V6. Stick with searching for the '86-'87.
Good Luck !