82 chevy rusty frame mounts ???

[wahl4m]

my 82 chevy frame mounts have some rust behind them! im thinking abou cutting/drilling rivet heads off /and remove the brackets and cleaning them up and remounting them? thought i seen somewhere a listing for a bolt with a oval head with some serations on bolt that uses a nut on back side to tighten up ?? seen them for big diesel trucks ,when they alter the wheelbase for body changes ?? i could just use flanged bolts/grd 8 ?? any ideas ??