Well, if you "bracket race it only", then the next question is "are you looking to go fast?"
- yes, the .474/280 cam will work. I've used that cam in a few 318's (street cars)
- I would run a quality 9.5 converter, on the loose side (3800 stall)
- I would gear it so that you cross the line 200 rpm's before your shift point. That won't be 3.55's. It will be around 4.30's - 4.56's
- I would sell both your intakes, and buy a RPM air gap (edelbrock)
- Yes, you can port the 302 heads. I'd advise it or they will be the bottle neck of your combo.
What E.T. are you hoping to run? What class?