Same recommendation as LA360. I used the small block 64277 damper with the external balance offset weight. No problem with the unit, no slippage.

I will say this though: double-check the process with the shop that'll be doing the balance for you. I explained what I wanted done to the shop I dealt with (1st and ONLY visit), brought them a brand spankin' NEW damper. Job was done, I went back to pick it up only to find that they drilled a number of spots on the damper to balance the assembly out!!

[censored]???

Basically, that's a one-time-use approach since I can't use this damper anywhere else if I want to have the ability to replace a damper should it get damaged!