i assume that its an 8inch converter? i ran a very similar combo to yours years ago that ran around 11.20. the heads were all done around 6600rpm.i shifted both gears at 6600 trapped about the same.you definately don't need more than 4.86s have you tried advancing the cam some more say around 102? a 2inch carb spacer always helped on mine also.how long is the header collector? it needs to be about 18inches running the rpms your at.thats a few things you might try once you get back on the track...good luck