How bad is it to run a 3.0L flex fuel ford ranger engine that has a tapping noise?

I have a 2000 ford ranger lte 4x4 with a 3.0L V6 flex fuel (can run 85% ethanol) and it sound smooth and good when cold, but when engine warms up, it develops a loud tapping. I thought it might be a bad hydralic lifter. I am not really sure. I changed the plugs and they were TERRIBLE beyond anything I have ever seen. I am really surprised it even ran. I bought it last week and it has had major neglect issues. It had rusty water in radiator. Bad wheel bearing. Bad nasty oil and incorrect oil filter. Bad wheel cylinder. I put new plugs, wires, wheel cylinder, wheel hub assembly, master cylinder, new oil and filter and drained and changes the sh*tty water in radiator and replaced with good antifreeze and water solution. The tapping is still persistent though… It runs down the road good now and has nice power, but it just taps… Any ideas on what it might be? Do you think it is a nasty lifter and what damage could be caused by driving it with a bad lifter?

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