lowest temperature cooling a 2004 town car a/c?

I doubt there is any such rating. The minimum inside temperature you can attain will depend on how hot it is outside. I can cool my truck below freezing........................in the winter.

97 mark viii lowers to 42 degrees F. Town down to only 50 degrees F although no leaks detected. Temperature here constantly hovers around 100 degrees F. Saw somewhere A/C range is 38 to 42 degrees F in general for cars without specific identity. Any credibility to that estimate?

If you can actually get the interior down to 42 degrees on a 100 degree day I would be impressed but I rather doubt this is possible. Maybe 62. Output temperature is not the same as cabin temps!

did reach 42 degrees on 97 mark viii. Guess I am lucky. Thanks.