IIRC, UV Mapper Classic is still available, still free...

http://www.uvmapper.com/

I'm no Mapper guru, I can't yet shuffle out-lying map portions into neat, neighbourly positions. But, especially for older OBJs that say 'template available on forum', but that's long gone, trying different un-wraps often gives a match to the texture maps. Because, yes, 'Classic' was so the 'GoTo' app...

Trying to find the teeny-tiny portion of a complex 2k or 4k texture that 'works' eg a vehicle's mirror, side-window or lamp, so you can mask emission and transparency, can still end up as a 'binary chop'. IIRC, my 'worst case' hunt took 19 tries...