I'd say 6500-7000. From there, you might need 26lbs springs. But with an aluminum flywheel (8000+, directly from their email, they have ran it 8000+)... Rod with bearings, great!
Overall... GREAT kit. Get 2 26lb springs though.
And do yourself a favor, and call ARC, and get a Super Dyno X .275 lift cam for $50.
I got mine. Great! Didn't even need to modify the block like AGK cams.