OMC looper combustion chambers - concentric or offset?

[Powerabout]

Always wanted to know what the story is on OMC loopers, some were made with offset chambers, 49ci, 44ci some made with concentric 56ci 31M, all v loopers
yet 2nd effort built offset chamber heads?
where should the plug be in the chamber offset or central?
anyone know?

[Mark75H]

Optimum plug position can vary with porting, compression and exhaust tuning.