It could be a variety of other things based upon what you have mentioned. Have you done any leakdown or compression tests to confirm? You could have gasket blown somewhere, tore up valve guides, and various other things. Its better to do the proper checks before coming to a conclusion. I am not ruling out bad rings, but its better to try and rule out the easy stuff first. Also would you be able to post pictures of your setup?
94 GT convertible - GT40's, F cam, Kenne Bell, Devils Own Meth Injection. (Sold)
86 SVO 9L - Mostly stock - 14.5@98mph (Sold)
New Project - 87 RX7 - 6.0, T56, etc...
New Stang Project - 94 GT Convertible 5.0, 5 speed...Stock