It bugs me that to do it right, you should send the new aluminums off to the machine shop to get checked. Now, not all brands are like that but a pair of aluminum heads that I could afford would need to be checked.
Quickly, the "twice a year sale for Chinese heads at 800+" turns into 1000+. I couldn't just bolt and go either. I have a friend that put pro comps on a 455 Olds without checking, and had issues.