We propose to observe four Crab-like supernova remnants, the
 Crab twin 0540-69.3 in the LMC, the composite remnant G29.7-0.3,
 the isolated plerion G21.5-0.9, and the plerionic core of CTB80,
 with CAM to obtain spectral index mapping of the synchrotron
 continuum emission, and to provide some of the missing spectral
 coverage of these objects between the radio and X-ray domains.
 The observing frequencies are near the expected break for the
 Crab twin and G29.7-0.3, and the spectral index maps should
 provide important information about the magnetic field structure
 and the site of particle acceleration.  We also propose to
 measure polarisation in one source, G29.7-0.3 for autumn launch
 or 0540-69.3 for spring, which would unambiguously establish the
 synchrotron nature of the emission and discriminate against any
 possible dust emission.  Finally, we propose to observe these
 four plerions with PHT-C to broaden the spectral coverage and
 look for bumps of thermal dust origin like that discovered by
 IRAS in the Crab Nebula.