Get the pro-x rod. I have had luck with the stock valves. I have used stock, wossner 13.5:1, and wiseco 13.5:1. I got great life out of all three of them. The wiseco finally cracked but it had a great amount of use. I also had used CP pistons once on it, and I had poor luck with them cracking early. But I had great luck with them on the ltr450 and my brothers trx450r.
Also use stock gaskets. Don’t be cheap. And also get a DJH manual cam chain tensioner. It helps deliver more oil to the head.