My brother has the 350ish (can't remember the displacement, 354?) kit on his, it definitely has a lot more low to mid range thump, but it won't rev like it did stock. The 300 hundred kit might be the best balance for that engine, but it all depends on how/where you like to ride.
The PO of that bike is a friend of mine. He went to the 300, barely broke it in, and then went to the 354. While he liked the lugability of the 354, he was a little disappointed with the loss of top end.
When he needed cash and decided to sell it at a bargain, I talked my brother into buying it, with the hope that someday he would send it my way when I have some extra scratch.