You'll probably need a bigger rear end, too, not just the 5 lug axles.
Basically have to rebuild the entire front end - steering and suspension, and upgrade brakes, like jlp said.
I looked into it when I rebuilt my I6, and I ended up replacing a lot of this anyway, but with I6 components. I'm at about $5K into it right now, and didn't touch the diff, axles, transmission, or brakes (other than a basic brake job and new brake lines). Not counting what I paid for the car and new tires/wheels.
If you're going to have to replace all of that anyway, it might make sense for you to make the leap to the V8. If it's what you really want, and you have the $, I say go for it, too.
Me, I preferred to go more the restoration route than mod. To each his own.
I can't answer your specific questions about modding the 302, but Good luck!