Horsepower limit for out of the box Edelbrock RPM heads

The person I mentioned with the 507 hp Eddy head 408 is waiting to get a set of TFS heads (when they become available) worked by and from Modern cylinder head. It’s someone I know from a long time back and am hoping to catch a before and after ride. Putting a Comp 275 XEhl in place of the PP284H when he changes heads, so I am really anxious to see the difference. The edelbrocks are stock other than quality seat and guide work with comp springs. I don’t know to what extent the TFS heads are being worked to yet. Swapping cams means its not going to be an apple to orange comparison. I am anxiously waiting for a break in the weather. I don’t want to miss the seat of the pants difference between the two to report back.... ain’t it awful when you meet back up with someone after 20 plus years and they have the combination like you want to build yourself?