What engine, internal balance? Have you checked where the pulley actually mounts? Although the ring is wider, i thought most were recessed in that area so a factory spec pulley would still work?
Update: Looking at some that are available i see that some do look thicker. Not sure how high dollar of a balancer your looking to buy. March did have some pulleys at one time that would work on some applications. I believe the Summit balancer will work with the stock pulley if that would be suffecient for your needs.
BHJ has some options, but they ain't cheap.....http://www.bhjdynamics.com/index.php?main_page=index&cPath=7&zenid=bk00ivpu9nugk46ip9nvfk7ne1
Other possibilities?....http://www.ebay.com/itm/Dodge-Mopar-SFI-balancer-damper-Power-Bond-318-340-/200214603986?
http://www.ebay.com/itm/PIONEER-872...pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr
http://www.summitracing.com/parts/PFS-90012/?rtype=10