As said by Don and Bob. Take the car to an independent shop and have them assess the system as it stands and give you an estimate for an R134a conversion. The original R12 condenser is not the greatest, but it will be (as Rolls-Royce say..) 'adequate' as long as it is leak-free. A new evaporator will go a long way to offset the inherent reduced efficiency of R134a as a refrigerant, but, again - you're in Toronto, not Phoenix. He can cope.

It sounds like you are putting a lot of cash into this to make it a nice ride for your son, yet he doesn't appreciate it. BTDT. My guy's 81 was the scourge of his life compared to the big-buck rides in the high school lot. (Numerous kids from wealthy families, MANY of them divorce situations, with Dad throwing dollars to gain favor...but that's S. California...) Now, a few yrs down the road, he's a little more mature, has done some work on the car, and it's still going strong at 295k where some of his cohorts have frag'd their rice rockets and BMW's. He's a Volvo believer now.

Your kid'll come around...and if not, trade the car for a nice set of walking shoes.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar MGB, and numerous old motorcycles)