Re:New Truck Build Chevy P30 need some advice...
With smaller rivets i use a drill to take them out, if you can't get a good handle on the grinder you may have a tough time with them. work slowly!
Try a drill that has a good amount of torque, get some bits that will handle metal- a hair bigger than the rivet, and drill them out. Start slowly to get a starting pint where your bit is slipping then get at it.
you can start with a smaller bit to cut into it a bit and have a starting point.
All my rivet removal i have done with drills, i am not that skilled with the grinder and find it can get squirrely or i end up cutting something i didn't want to. Especially in a tight space like what you are working in.
best of luck