Hmmm,,, yeah I see what you mean. You all ready got a good torquer and now looking for something different. I can dig it. I was shifting at 6500 or higher with my old motor and it was NOT "falling off" at that rpm I can tell you! It was an awesome motor and I have a feeling it was good for 7000 +, but I didn't want to risk it.
I wouldn't know what's good or bad for rpm at or above 6500. Of course ARP, good valve train, rods, etc. are a must have. Two bolt? If Keith says it will live, I guess it will. One thing I see repeated quite often is: You can have high rpm but it WILL shorten the life of your motor. Most of us don't put "that many" miles on our replicas, so maybe that's not a major issue for us?
Say you go with a BIG cam, will the heads and intake support the flow? I was (still am) running high rise heads, no doubt THEY would support the flow. My previous cam was a solid roller. On the tear down I found that all the clearances were on the "loose" side, very loose. The motor WAS built for max horse power and a short life!