ok, i know a bit about this topic...
i have a "buddy" running something like what your talking about. theres ramsey crap and theres good stuff. theres a guy in san francisco thats a retired engineer and he builds these things for different applications. yes, they may exceed certain regulations which im aware of and could care less about discussing all the better things our government can go crack down on so dont even go there.
in order to get something that sounds truly beautiful you need something built like a true AM transmitter and not some ramsey kit. the unit im familiar with uses a 6bq5 as the transmitter output and uses a hammond audio transformer being fed by a gainclone amp for modulation. transmit freq is set via an internal synthesizer. it makes AM sound like mono FM. bigband playing through a unit like this onto a vintage radio is like a time machine. use an old laptop running some volume leveling software with the audio player of your choice. winamp works well with a volume leveling plugin. itunes will work also as it has auto level adjust if you dont mind apple controlling how you move your music from one place to another.
on the music players eq, knock down the first and last slider all the way. no sense in trying to reproduce something that wasnt really part of the "sound" back then.
a transmitter like this will likely set you back a grand if you have someone build it but the sound is just indescribable. antennas are another issue. i'll get into that if theres interest.
if you're not up with flying the pirate flag theres this option...
http://www.sstran.com/
pricey yes, sounds good, so i have heard but not as good as the transmitters with actual modulation transformers and less forgiving of antenna issues than transmitters with tube outputs.