Sorry to hear of your misfortune. I cross my fingers every spring when I start relying on my 124 a/c. So far I have been lucky, knock on wood.

I have always been a skeptic of chemical cures for leaks and other mechanical ills. I also know that the 124 car is a very poor candidate for converting to r134. You will lose cooling capacity big time on these cars.

As Steve Brotherton states best, R12 is the least expensive component of your air conditioning system, why is everyone so intent on changing it?

In your case, R12 is REALLY a small expense as a percentage of the repair. You can now buy R12 for about $29 per can. If you have the evaporator changed by a shop the R12 will probably be less than 10% of the expense.

I recommend that you bite the bullet, change the evaporator, evacuate and charge with R12. I would personally not consider ANY alternate refrigerant for this car.

My $0.02,