Buy a used one to save some cash right now, but don't try to cheap out that much and glue it on!! 10lbs of steel turning at 5000 rpms is a lot of momentum that could punch a nice dent in your hood, rad etc.
Mine shifted (cracked all the way around and rotated about 10°) on my 72 340 (externally balanced) and caused terrible vibrations. God only knows what extra wear that did to the bearings.