Anthony What's up 1020 Felpro with Hightack is what I used. The 1020 has be listed for the 427 bore for 20 years if not more. What was on the engine before? ASk your builder what he used. I would use the Hi tack with Alum heads and iron block because of the expanding rate of the different metals. Send me an email with your number I can call. What did you find on the motor. Make sure you put the gaskets on the right way.
Rick Lake