Congrats, I too would be excited to get that for what you paid. It really doesn't look that bad IMHO, now the one Drivesitfar posted, dang man.
I'd start with a quick hose wash, dry, then a cup brush in a angle grinder to knock the loose off. Soak with penetrating oil if needed to get all parts broken down. Then evaluate from there if you want to media blast or electrolysis tank it. I'm a fan of the latter, but your choice.
The hot tank Davefr reffers to is a hot caustic soultion dip, it is good for stripping everything off of a piece of metal. Hence engine rebuilders and radiator shops use it to throughly clean parts. However it doesn't do that great of a job removing rust. It is a process more designed to remove grime, paint and soot/sludge.
here's the Prentiss before straight store bought vinegar and after 3 weeks to show what that can do.
You win
, where did that thing come from?
What on God's earth had the previous owner inflicted upon it?