IMO CL is for unloading stuff locally in exchange for selling at less than max possible value.
I learned not to post anything for free, even if I give it away. I'm sure there's other ways to reduce the scammers, theives and those who just waste your time.
For a poly engine, I'd say you've got to be patient and work auto listings, car clubs, shops with a higher than average percentage of people who might want one.
I unloaded a '65 727 on the transmission shop for partial value on a later one. They were glad to have one in their stash and I got rid of an oddball, sorry rarity, taking up space.