I do not know much about engines but the others did not reply to this...
Depends on what you call "best".
The Lycoming operators' manual gives some useful information:
The O-320-B series and -D series are rated at 160 hp at 2700 rpm
The compression ratio is 8.5:1
Weights of 320 engines run 272 to 307 lb. In the B and D series
they run 275 to 291 lb. Those weights include everything like
carburetor, spark plugs, harness, starter, alternator, etc.
On most 320 engines the height is 23" (22.99) (19.22 to 25.57"
in various models), Width is 32.24" in ALL models, and length is
29.05 to 33.59"
The LIO-320 series runs backward.
I hope that helps.
