I would look at either Edelbrock heads with 70cc chambers or Dart Pro 1's with 72cc chambers, or better yet, AFR 180 heads with 75cc chambers. See if they would bring your compression down enough so your DCR (dynamic compression ratio) is under 8.5. With the right cam you can run over 10.5:1 static compression as long as the intake valve closes late enough to create a satisfactory DCR.