I had this very same problem on my Mopar Performance 8 bolt 4.15 stroke crank for my 493 build. The problem ended up being the machining on the snout. the snout was not machined 'back' far enough. The crank gear lined up perfectly fine with the cam gear but there was about 3/32 to an 1/8 of 'shoulder' showing on the snout. I ended up machining the hub on my balancer to fit over the shoulder and rest against the crank gear. Worked very well for me. Next option would have been to pull the crank and have the snout machined correctly.