My thoughts would be to fix what you have, it doesn't really look that bad.
In fact, if you did remove it to fit another, I think you'd still be miles better off repairing that one once it's out.
It's a bit of a job to remove and refit, and there are some pretty good rust treatments available.
If you wanna sell that one... I'll buy it and fix it!
Cheers
James
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