Any modern engines or engine builds for modern results?

So, what were you looking for? Power has little secrets. High flow heads, valves seal, rings seal, good fuel metering, good ignition. New cars add overdrive(s) to cruise at a sweet spot at a lower rpm. Steady on the gas, keep your foot out of it. Small blocks should get 20 mpg, geared right and tuned. Even big blocks would approach high teens with a TQ and 2.76 gears. Magnums would be the easiest, same exhaust and almost everything else. IMO the key is an overdrive. Everything else is more complicated than it is worth.