Depends on the rifle it's going on.
Some require a lot of care and fitting. Examples can be Pre-64 Winchester M70s, 1917 Enfields, SMLEs and Springfield 1903s They have to be set up to time correctly and clear the extractors. Most autos other then the AR15 are also in that class.
Others like Mauser M98s, Remington M700s and Ruger M77s are very quick and easy.
So saying "new action" doesn't give enough info to answer the question.
They don't make pre-fits for these
I wouldn't install one on even a custom action unless i had a head space gauge, though
