This used swivel base is for the older (pre-2008?) Econolines. Has a seat belt mounting bracket, which is optional. "Universal" floor mounting bolt pattern, so might fit other applications. Needs to be cleaned up and lubed before install.
$130 in Venice, CA.
I'm leaving back to Tucson on Thursday the 22nd, so might be able to meet at points in-between, if you're not in the Los Angeles area.