To bad you guys aren't around St.Louis, MO. I'd do it for free. I love working on J1 model carbs. Could do the whole job right, in about two hours.
Just remember that a Jet Kit is more for tuning mid-range power rather than max power, if you simple want a higher HP number, install a good exhaust (or run open header, hehe, thats what I like), +4 advanced rotor, and 160ish size main jets.
If you want a GREAT running J1 bike, then look at my previous posts. or shoot me a PM
I haven't used Ivan's, but Dynojet has always performed flawlessly, and I highly recommend Dynojet jets over Mikuni, their venturi design allows for smoother transitions into the top-end rpm(really though, thats something that most riders wouldn't notice).
Do your self a favor though and try a #15.0 pilot jets, usually this will give a MUCH improved throttle response. (works best with free flowing exhaust or open header and +4 advanced rotor)