That's hard, Darlington is very special and I haven't been there for a while...
Well, I'd start with the clear 70°F setup and try the following changes:

Qual trim:
Drop diff ratio to 3.800:1.

Race trim:
Drop diff ratio to 3.800:1 and reduce tape to 40 or 45%, you need to check that yourself. I don't think that you have to change front bias or any other handling-related settings.
Furthermore, you might want to tweak the gearing, you need a gear like 6.5:1 for good restarts.