My 1939 GE HM-80 has the earlier FM band, 39.5-45MHz, and I am able to receive a few strong local FM stations. I suspect this is due to the harmonics in the LO. Because of this I have never got around to making a converter for this set. I also have a pair of Meissner's, a 9-1047 pre-war and a matching 8C post-war. I used to have quite a few more as I collected pre-war FM's at one time, but this is all I have left.
I do have a converter that is shown on the FM Only site here:
http://www.somerset.net/arm/fm_only_converters.html
It's down the page a little under the Crystal Devices heading. It is completely passive. I haven't gotten around to trying it either so I don't know if it works, or how well it works.
Darryl