One of my current projects is a 70s style rock / hard rock act, and we regularly play DP / Rainbow covers (among other stuff), so I can give you some pointers. Not exact settings, since I'm not trying to replicate Blackmore's exact sound, but this should get you pretty close anyway:
- Use the Edge mode. Crunch sounds too dark and modern for Blackmore's 1970s sound. Edge will get you in the ballpark easily.
- Use EL34 power tubes instead of 6L6s. They have the right midrange character for this kind of music.
- Try a single coil-equipped guitar (like a strat) instead of a humbucker one. Well yes, Ritchie also used humbucker equipped guitars at least early on in DP, but I can find his characteristic sound more easily with single coils.
After that, your fingers will make a bigger difference than your amp setup will.