I have a similar McLeod flywheel that I bought for my 59s 428CJ.. It came with a bolt on counterweight with 2 countersunk Allen head screws to attach the supplied counterweight. I just assumed that was how all the later McLeod flywheels were, both my FE and SB Ford aluminum flywheels also came with the weigh and screws in the box. Years ago, my McLeod 428 flywheel had the imbalance build into the flywheel, rather than a bolt on counterweight. Or is the current 390 and 428 flywheel identical, except if you request a 428 flywheel, they throw the counterweight in the box, and leave it out otherwise.