The BHJ balancer is a lot heavier than the stock balancer.
The biggest gain you will get from any alunimun underdrive
pulley set,Is mostly gained from weight savings from the
aluminum underdrive pulley set.More so than any gain
received from the gear reduction because of the smaller
or larger diameter of the pullies.
For max performance from a aluminum underdrive pulley set.
Its best to use a stock aluminum & steel balancer.
The BHJ balancer will rob over half of the weight savings
gained from the aluminum underdrive pully set.
But with daily use the heavier balancer BHJ will help make a
crankshaft live longer.The extra weight on the outside
diameter of the balancer will help to exsorbe more shock
waves from the crank.
I don't run the alternator pulley,and works just fine.
Randy