Steve, if you must, pulling the whole dashboard out to access the AC evaporator takes only an hour or so (4 screws, tach & glove box removal). Reinstalling takes a day or so.... I've had ours out twice. There's a How-To article in the POCA Archives.
If you're gonna use r-134a freon, you should R & R the evaporator valve under the dash near the glove box (accessible). The OEM valve is calibrated for R-12 so freon flow is less, and usually has a small cone-screen inside the 'to' line leg of the valve, that is plugged solid with rubber flakes & mung but is cleanable once hooked out. Most guys leave it out to increase r-134a flow a bit more. New valves don't come with the screen.
You should also R&R the dryer can in back regardless of which freon you select, as age & flow reduces the dessicant pellets to an awful looking black sludge. And finally, many owners add a compressor overpressure safety shut-off switch. Ours blew an A/C line outside of Bakersfield that oiled down the inside of the windshield at 90 mph & sounded like a rifle shot....
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