Stick with the 454 R. I have a similar combination. Same heads. I started with an Eddy 2927 thinking it needed that. Something wasn't right. I had to get into the lifter valley a couple years ago and decided to install an Eddy 2908 (Morrison modified 2907) I got in a horse trade and the car came alive.

Now before one says but, that's a CNC piece, don't. They didn't do squat. However, the port match was perfect to those heads. You can do that port match yourself.