Know this thread is old but you may still be in need. I got the same plates as you need for my 50. The plate is actually a 47 and you'll need a metal 48 tab that goes over the year as they used that plate for 4 years. I got mine from a guy at the Long Beach swap meet. The big vendors are HIGH like $250. This guys sold them to me for $100. He's s small plate collector/trader

Bob (323) 721-2258