1. I love the people who say they can buy an Aircraft Engine for some
small amount of money and bolt it on and go flying. What they mean is
that after decades of search they managed to flam some widow out of an
engine for a tenth market price, they bought some oddball no one wants,
or they have an engine that is such a mutt with no logs and bootleg
repairs even the airboaters eschew it. Good aircraft engines, such as
they are, are worth a lot of money if they are airworthy certificated
engines. If you have one, it's generally economically more
advantageously bolted on the front of a certificated aircraft.

We all know you can weld and machine about anything and all the little
tricks, or most of them anyway. There is no consistent source of safe
aircraft engines below market price. Even if you are willing to
generate very fictional logbooks, like most of the FBOs I know. It
isn't that hard.

2. If the Lycoming and Continental paradigm of large displacement
light slow turning engine was so great for aircraft, they would be
great for a lot of other things as well. Teledyne Continental and
Textron Lycoming have absolutely no interest in marketing or developing
their ridiculous museum pieces for any other markets whatsoever. The
reason is simple, no one likes being subject to ridicule. Which they
know would be the case.

3. "All the people who use an automotive conversion spend fifteen
thousand dollars anyway". You are comparing apples to oranges because
the guys spending like this are going all out and not doing any of
their own fabrication. And ignoring the fact that their per hour has to
be a lot cheaper because once done rebuilds have to be radically
cheaper.

4. "You are in all reality only going to fly it a few hundred hours
anyway". Well if that's the case, join a flying club (a real club) or
just rent an airplane.

There are others but that's enough for now.