that depends on the user. What you don't want to do and what others will could be different. Some don't dare back half a car others look at it as a minimum requirement. So it's all relitive. And even with a port mismatch of the 5.7 intake to the 6.1 head is not that bad. It has been done many many times. Usually the other way around ie a 6.1 manifold on a 5.7 head, but it is doable. And if you open the ports up some it's better than nothing.