I know nothing about them, I do know the following groups:
I've used these for nearly a hundred dealer locations / feeds for many, many thousands of
used vehicles ads on CL and measured lead conversions and sales through CRM path analyses.
https://www.hammer-corp.com
They don't look bad, but make sure it's native, proprietary software because a lot of group white label and it could be one of the two aforementioned. I know, as I plan on partnering with
LotVantage in the future for a project of my own (market adoption segment), in order to leverage their feed to CL technology via API.
CL now charges per vehicle listing, so there is no longer a ton of SPAM, etc. I'm not really sure what you had meant by SEO in this thread's title though. These are paid ads on CL. This really nothing to do with organic optimization.