If the 555 intake bowl looks like a 379 head's intake bowl, that's bad. If it's smaller than a 333 bowl, that's bad. It is not difficult to see the difference, it is a big difference. In fact, there is not enough port wall thickness in a 379 head to open it up to a 333/817 head bowl size. This is something I checked with my sonic tester a few years ago. The 333/817 (and possibly 1147) is so much more advanced over a 379 it is like it was designed 25 years later. Again, just my opinion.