9 inch front left side drum Richardson, TX

Ok. I know the spline wedges the drum to the hub, so when you take the wheel off the assembly stays aligned. In my opinion you could get a new stud, clean the hole up as best you can and use it that way. The other 4 will hold the hub and drum and then the 5 will sandwich them when you torque the lugs down. Unless the hole is really hogged out I think you will be ok. I once converted a 4 inch drum set to 4.5 by using a wheel adapter as the drill template. I just flushed the old studs off with a grinder, left them in and then pressed the new studs in. Never had any troubles.