how do you clean up a used engine

Here's what I did "last time" good or bad

Pulled the VCs and pulled the rockers off. What this does is, to allow all the valves to close.

Of course put old plugs into the plug holes

I "burned" a ratty old distributor--just put a couple of plastic bags over, and duct taped the **** out of it

Built a plate for the carb inlet, cut a ratty gasket out of a filter box and bolted it on.

Took a pair of old VCs and plugged all holes, then glued gaskets on one side only, and oiled the engine side of the gasket.

If you can, pull all the freeze plugs and drain plugs., get your pressure in there along with scraping tools/ wire and scrape as much gunk and rust as you can

I also pulled the water pump. Be sure to "washer up" and reinstall the pump bolts to keep the timing cover sealed.

Then just take a good look for unwanted openings into the oil system, make sure the sender and dipstick is sealed, etc

And that avatar...............LOL