Just wanted to add a little info to the conversation. I ordered the GM of Canada docs for my Baltimore LS6(sold new in Canada) back in 2009 to confirm the car before buying it.
Once I got the car, I received more paperwork from the seller he ordered dated March 24, 1989 from a "Roy J. Mercer"-Customer Assistance Advisor and having "General Motors of Canada Limited" letter head. This was apparently before the Vintage Vehicle Service existed and George Zapora ran it and was hand signed by Mr. Mercer. It also came with a sheet that listed the Date, VIN for my car, Trim, Colour(Canadian spelling), and then the options for the car. Luckily for me the paperwork also came with a waxy copy of the original microfilm import invoice dated May, 1970 which lists my LS6 as well as 2 others, a LS5 vert that still exists today and a bunch of station-wagons. The LS6, convertibles, and stationwagons weren't produced at the Oshawa, Ontario, Canada plant. And yes the key codes are listed for all the cars on the sheet.
As far as the 231 number being imported into Canada. Dale points out not all of these are LS6 cars. I recently sent Dale info I found on 3 L78 Chevelles imported into Canada. I found one locally with the GM of Canada docs that is a white/black stripe L78/auto/4:10 car. I'll try and get the owner to post the car and docs.
What I find really intriguing is with (I'm guessing) less than 200 LS6 cars coming to Canada, why would the first LS6 "pilot" car go to Canada????? Wouldn't it be a very hot commodity State side? I would think factory racers, GM Marketing, GM big wigs, etc. would get first dibs on the new LS6 cars as they came off the line.