I do not do this for a living, but will offer my take on it anyway.

- Normally I would suggest that you keep an R-12 car as an R-12 car. I believe that cars coming from the factory as R134a do quite well, but they were built from the ground up as R134a cars. Unless the entire system is changed out during conversion, you have a mixed-bag of R-12/R134a components.

- Some say that the heat transfer capabilities of R134a is not as good as R-12. That may be the case in a converison scenario. I have a 2004 base model Tacoma pickup equipped with R-134a(from the factory) that blows 40F air on a 100F day. Go figure. BUT....you live in Canada and I doubt you have to deal with the temps that exist in the lower half of the U. S.

- I respect Steve Brothertons and Larry Bibles observation about the drop in price of R-12. Having the credentials to purchase said product, I am now paying about $10 a can less for R-12 than say a year ago. It has indeed dropped in price. BUT...you might be considering a trip to the U. S. where a shop would repair the leak(hopefully) and recharge. Larry has mentioned $14 a lb. R-12. In cans(from Larry' source), it's a hair over $20. Not too bad considering the rising cost of R-134a. Now comes the hard part.....getting a shop to sell you R-12 at a price that's even remotely resonable. I know for a fact that shops that still service R-12 systems(they are growing fewer and fewer as time goes on) charge WAY more than $14 a lb. You wouldn't believe the price being charged in a lot of these places. You'd spend some big $$$ recharging with R-12 and then be faced with the possibility of a return trip at some point in the future.

- SO...unless you plan on coming down yonder and studying for the 609 exam(not sure a Canadian could do that?) and finding/fixing your leak in a hotel parking lot, I personally believe you would be better off converting to R-134a.

Your circumstances just don't support an R-12 conversion.

My 2 cents.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"