You need, at a minimum, a 10 X 36 lathe, with a good size through hole in the spindle, that can easily take a large barrel through it. The main thing, though, is installing the lathe. It has to be on a good, firm, and level base. If the base isn't level, it will throw the lathe bed out of level, and it can be enough of a twist to cause it to cut a taper on a straight part.
On phase converters for 3 phase motors, you need to remember that you will lose 1/3 of the HP of the motor, when running it on 220 VAC. That is if you're using a static phase converter. A rotary converter will give you the full motor power. Some lathes, though, are coming with reversible single phase motors, which will give you full torque and HP during operation.
Grizzly has some decent prices on lathes in this range, though I haven't tried one of their South Bend models, the others I have.