Do you have any old junkyards in MO? This is where I would go.
We have several here in NC but I'm not risking a snake bite for parts I don't need.
You can also try searching ebay.
https://www.ebay.com/itm/392972309769


"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."