One offs of 20year old installs are not giong to cut it. Yes, the LS1/2/4 is a good solid motor, but not in the power/weight of the 4 place sub 200kts cruiser. I don't see diesels getting the weigh down for a 2-4 place plane. Once you get out of the 150-160-200hp range engines are plentiful. But the market really is the 150-200hp range. If the FAA would allow a company to license O-360s prints to clone the engine you could put out a to-print-spec engine for less than $10k. You can get a custom one off forged crank for less than $3k. Yet new O-360 cranks are $8k with a $4k core. NO. Its not about low production numbers. Its about holding the market hostage with FAA regulations. I wonder if the Magnuson-Moss act would apply to aircraft???