Sorry to hear you lost an engine. I have a always rebuilt the old one, but in this case I agree with those that say get a new one.
The missing oil is basically why in the old days (and when you’re using an old vehicle you are essentially back in the old days) we used to check the engine oil with every gas fill up.
Once you determine that an engine has normal oil use, you still checked it every couple of weeks, or less.
Yes oil burns and goes out the tailpipe, oil leaks in small to large areas (but you notice a large oil leak usually), oil gets sucked out and burned through a badly implemented PCV system, past the rings & valve guides and some oil will disappear just in normal use.
The older the engine is both in design and age, the more quickly it uses it.
So even when you get your new engine you should check it fairly often compared to a modern vehicle.
Especially when it’s new.
Buying a wrecked Explorer for cheap and using the engine and other associated parts is a great way to get a good engine. But it’s a lot of work and not usually something that people do when they don’t have all the tools and time and experience to do it themselves.
You can hire someone to do it if you find the right shop, but there’s the kicker too sometimes.
Depends on where you live and what type of shops you have around.
As they alluded to above, companies like Blueprint Engines are well thought of and have some good options, but from what I understand they are pretty far behind getting an assembled engine shipped out. Possibly the same for most rebuilders but we haven’t heard news about many of the others lately.
Since this probably isn’t your daily driver anyway(?), waiting a few extra months to get what you want may not be the end of the world.
Sounds like you might as well check a few places, including local AutoZone at O’Reillys stores, determine what you want and place your order soon just to get in line.
With any luck someone will have what you need fairly quickly if you’re not trying to go too exotic.
Maybe stock is easier to get and most of our long wait stories are only about performance engines.
And let us know if you find anything because others might be looking as well.
Good luck.