It should cost you very little to have a shop drain your system and reclaim the r12. The shop that did my '90 10yrs ago did it for free, simply to get the r12.

I personly had a poor experience with my r134 conversion. I found that while it cooled things off, it never made the truck that comfy on a hot humid day here in CA. On days when the temp was above 95 it barely made it tolerable, and if above 100 I did just as good to roll the windows down. Since I removed the r34 refrigerant and replaced it with Maxifridge it cools things off almost as good as the r12, it actually gets cold enough on hot 100+ days that I have to turn the fan down.