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Yes those prices are a little eye watering.
I would try to rig something up to test yours.
If it's been disconnected for years there is a higher probability of it having some corrosion and leak. If it's been in use, or in a sealed system until lately then it might be just fine.
If you could find a way to either pressurize it or put a vacuum on it and it held that would be a good enough test.
I recently had the same question regarding my 78. I did a vacuum test on the evaporator and it didn't leak so I cleaned it up (inside and out) and re-fitted it. When I came to fit the new accumulator/dryer I had to bend the evaporator inlet tube just a little bit to get things to fit. The system then wouldn't wouldn't hold a vacuum and it turned out that the evaporator inlet tube had developed a very small crack where I had bent it. On closer examination I could see that the tube was slightly corroded in this area, which is probably why it cracked. Fortunately for me 78 evaporators are not expensive ($46 on Rockauto)
Well you didn't really mention if it's 77 early or 77 late. they are different. Early 77 was VIR system. Late 77 is the same as 78 and up.
I have the early. Converted with VIR eliminator orifice tube block and accumulator. Modern compressor and parallel flow condenser. Etc, etc. I recently ran a thread all about it.
None the less. My evaporator is just fine. never needed to touch it.
So just because it's 45 years old doesn't mean it's bad.
And I don't understand why no one can test it.
seriously, any good radiator repair shop can test it and repair it if nessesary.
From a well known Corvette vendors web site.
As you can see 77E and 77L are different. But only 10 bucks different in price.
And yes they can be pressure tested as can a condenser or a radiator.
1977 corvette Evap core
