I never ran rares, but I would imagine an AspX is probably the best all-around ship for that job. Since you are asking about the Keelback, I would say that it could do the job, but you would probably be better off in a Cobra Mk3, or the AspX. The Keelback probably requires a fair amount of Engineering to be competitive, but I think it would still fall short of the other two I mentioned, even if they are just A-rated in the important parts with no Engineering.
Hopefully an experienced rares runner will pop in here, and give you a better answer.
Riôt