To my simple mind, the technology is essentially the same between prewar FM
and "new" FM. You would change some coils & whatnot, primarily in the front
end (experts, chime in here as usual to correct my habitual blunders :-), to
receive and decode the same kind of signal, only in a different frequency
band. You would also want a dipole antenna of slightly different size than
what's used now. Otherwise, I see nothing to prevent you from building a
"new FM" receiver using prewar components.

Phil