I bought this one from Mancini. It is called a Pro Sport balancer and I believe it was about $190 and it is for internally balanced engines. I had one on the old eng for over 2 years with no problems. All the stock pulleys fit and it lined up the crank pulley correct with the belt. It is really a nice product and it is made in Austraila. I like it as it was on my 440 and this new one is on my 493 as I left the old one on the 440 since that eng is going in my buddies car. Ron