People have definitely started with worse, but if you're not worried about using non-original pieces, a 4wd tub can generally be found rust free and for 1200-2000 shipped to you from out west....maybe even less. It actually is better to find a roller that's cheaper to transport. Might be able to find one for 800-1000 and pay 4-600 to get it shipped if you can catch a transport on uship.com or similar....
Like I said, you can always just get patches (from a vehicle out west or new repro) but if you're not concerned with the originality, you'll probably come out ahead money wise and most definitely time wise by starting with a better tub.
IMHO
It's always more fun to spend other's money...but in this case I think I'd be saving it...