well if you unwrapped lod0 (the higher one) then smashed it down to meet the requirments of lod1 it should have the uvs good already. If not and somehow you need to transfer uvs. I don't think you can since the vertex order is now seriously different.
Finished the Ember Spirit blades by Doubleleaf. Tomorrow promo thumbs will be done and submitted. One note is that the particles system for Ember is bugged. Since it both forces a vertex based particle and the default weapons particle when importing. So I had to override that with an empty ember weapon particle which…