Wait for the next downturn, its coming and its going to be savage, then pick some of the pieces you covet at sensible prices from forced sellers.
In 20 years this stuff is going to be valueless:
I had 30 builders and cab plates five years ago, I now have 5, I have kept my favourite five and my daughters can send them to the metal recycling plant when I expire.
I have also thinned out my collectable high end brass for the same reason.
opinion (with a healthy dose of reality).
nick.