Have some questions.
Sounds like a good combo.
1. I'd go with the 670 if you aren't going to be running on the strip.
2. 2500 stall would be more fun IMO.
3. I have no idea what your 02 Ram sounds like, but, I put some cheap $15 Super turbo mufflers on my truck from Pep-boys and it is a pretty mellow sound, I like it.
4. I'd guess 275-300
5. Never used an MSD box, but I used my stock distributor with a Crane box just fine.
Just my .02.