As already mentioned, the definition of "decent idle" varies a lot. If you want to be able to idle at 600 rpm while balancing a quarter on your air cleaner, that cam isn't going to do it. My 451 has 272@.050 solid and it idles "decently" at 1100 rpm. Some people are running even more cam than that on the street...

Anyhow as you say, it's better to have this in-depth conversation with your builder before the project is complete...