the stock ones are die cast
the vortec head bolt pattern is somewhat different than non-vortec heads so other brackets dont exactly work.

For one motor, we made an adapter plate that bolted to the head. Then, we transferred the bracket pattern to the adapter. This pushed the belt pulley out so we had to make an equal spacer for that.

On another, we cut the die cast vortec mounts so that we only used the a/c compressor half.....not the p/s lower half. Then, we powder coated the bracket in black wrinkle....it kinda disappears but it is still big.

mike in tucson