In fact, the fake MRF497s are actually MOSFETS as opposed to bipolar transistors, and they catch fire as soon as you apply power to the radio if you try to use them to replace a failed MRF477 in a Lincoln. I did try one, and got my money back.
Keep a look out for genuine MRF497s because they are a higher power rated version of the MRF477. Totally pin and circuit compatible.