if i got the howell topend kit and a haltec sandalone would i be safe to raise the revlimiter and get another 1K? would there be any hp benefit?

Depends on the cam spec and how they make their power. What's the need for an 8000 rpm redline anyway?

Yes there would be a benefit, if you wanna keep close to stock idle get the #12 cams, if you want to really make power get the #16cams or the #18 if you have high compression. One problem you might have is engine loads, if the engine isnt balanced or you dont have a rebuild kit for the bottom-end you could end up breaking something, I know from 8k-9k rpms engine load doubles so who knows for 7k-8k. On another note if you really want some power look into some quad-TBs with those cams, you could see a 70% power improvement which is a fairly big jump. Good Luck