Those are nice but man they kick in quick. MP has a few different ones available in different spring tensions also. Forget the colors but white and green are pretty common.
The colored MP ones are for the electronic pickup distributor with the Mallory advance. Mopar Performance does (or did) sell a pair of very light DC springs for drag racing. They are even lighter than the primary spring in the tach distributor. My guess is they were originally for 1/4 mile racing with points distributors.
Being that this is an all original car, unless the goal is to only use it for short drives (1/4 mile down, about the same back), I'd work with it as is. I think its pretty sweet you're tuning it with the original dual point.
One difference today, over back then, is the fuel. So first I'd run it as close to factory spec as possible and see how it does. That's a pretty solid baseline.
Then see how it does with a bit more initial timing (shifting the whole curve). Mostly because its the easiest to do.
There's two things to test here:
One is everyday driving. Try on it on the highway, and when its fully heat soaked, listen for any pinging on part throttle (uphills or mild acceleration or both). If so, note what rpm and load (vacuum). Then you can tune around that.
The other is wide open throttle in top gears. Do this at the strip. See if it likes more advance or not. Probably will, but if you hear any pinging, or see any signs (specs of metal on the spark plug porcelain), then you've got to back off the timing. Also if you keep advancing and there's no gain in the mph at the end of track, then there's nothing being gained by more advance.