[jimbosprint]

I think most leaks are usually in the old o-rings, not in the evaporator box. I plan to use the same evaporator for R134a, and replace everything else. There aren't any AC parts under the dash except the controls and ducts, so you should be able to get to everything with refrigerant from the engine compartment. I am not sure if it is possible to get the evaporator box off the firewall without taking off the fender, but I plan to at least remove the inner fender. You may not even need to take it off, but mine is full of leaves.

Old Air Products was helpful when I called and asked them about the upgrade to modern refrigerant. They have knowledgeable staff and parts that bolt on without customization.