350 parts are so cheap now I think the 350 would be the way to go.
I spent months researching my 400 build. I went online and read everyday. If you are going to spend the cash at least do enough research to get rough cost estimates of both builds. Why not? Unless you like making huge mistakes and wasting money.
305s are okay, but 350 are better overall. They are a good compromise between mileage, power, and torque.