If I was going to go with a transformer, I would go with 2. Step that up to 480 and back down to 120/240 but at that point bigger wire would probably be cheaper. Trying to boost the drop up at the far end is just paying extra to hide the waste heat you are losing along the way.
#1 al would get you in under 3% and probably not break the bank. #2al gets you up to 3.3% but that assumes 50a load and that would have to be a peak. I bet 40a would be a better working number. If you do that you can get in around 2.5% with #4 copper or the #2al.
