You still haven't told us what you want from that vehicle. Is it going to be your daily? A racer? Or a Hotrod for roasting tires with shiny bits on it? The type of stuff to put in varies enormously with whatever driving style you're aiming at. Going 350 is certainly a good idea for a rod (many cheap good parts available), but if you're planning to cruise with no extras, then the 305 will have it all (less work switching gadgets). If you want to roast tires get a higher gear, if you want to cruise, get a lower one. See what I mean? In general what you're planning is far from being a bolt-in, so you want to think about what you want from it and plan carefully. But that's just my advice, the more we know the more we can say.
Just thinking loud...
Good luck,
Mad