LA 360 vs. 5.9 Magnum damper weight specs?

I'm grabbing a 5.9 Magnum short block to put in my '70 Duster and I want to run the LA timing cover setup which I already have, thus V-belts. The engine I'm getting has the one-piece damper and crank pulley so I'll need to use a different one. I have a Summit SFI damper with the bolt-on counterweight which I was running before on my LA 360. Does anyone know the weight offset specs for the two engines, I know the Magnums have less than the LAs but that's it. I'd like to drill out the counterweight to match a Magnum engine if possible, it would save me $100 for a new one...?