...the most trouble free conversion is probably done using Phil Wood 26tpi rings and the proper Phil cartridge BB. But they're not cheap. I've never used a VO threadless. I have done at least one conversion by reaming and rethreading to Italian, but it seems like a lot of work and requires some tools that would cost you more than the Phil conversion.
The MTB spindle with the old cups and bearings works fine, and is cheap, but IME the availability of those spindles has gone by the way. Maybe someone knows of a source, but the last time I did one, I looked through an entire bin of spindles at the co-op and found only one that would work. You might increase your available universe of spindles if you were willing to face the BB down from 71 to 68 mm. It's only 1.5mm off each side with a facing tool. But you can't undo it once it's done.