Have some questions.

Whitey, I had a long winded resonse, but I hit the wrong key and sent it into the great beyond. The short, short version..
670 CFM is wet flowed, MPs 750 cfm is dry flowed..they are the same result. 770 will be much to big a carb.

Power brakes need vaccum during cruise and idle. You always have vaccum during decel. Vaccum during full throttle at rpms over peak torque mean you have too small a carb.

TCI as a whole stinks. MP convertors from Mancini Racing are cheaper and as good a product if not better. Dynamic or PTC would be my top choices, and I wouldnt go higher than 2200 with your current combo.

Flowmasters rule. I love them. But you will not have a sound anywhere close to a Ram unless you add resonators or cats ahead of the X pipe. I like SUmmit or Dynomax bullets for the resonators, then the flows out back.

Where were you looking for 3.55s from? I'm pretty sure they are available right now for most center sections...