At that level, a Z transmission probably is his best bet. I'm sure he could find one lurking on ebay or put a wtb ad up on some Z forums. The axle recommendation is a good one too since it seems the stock axle limit is somewhere around the 400whp marker before they start snapping. You can pick up some new ones from the Driveshaft shop that should hold close to 650hp. The axle bars will run you $550, and if you want them to install them in the housings it's an extra $150.180fan wrote:yes, consider getting the z transmission. the sr one will hold, but it's a matter of time before it goes. At that much power, consider getting new axles as well.