[JSeery]

A 49 should have hardened seats, but I would check with the builder. The fuel octane is going to depend on what you have done to the engine. Most flatheads are very low compress unless something has been done to increase it and even than low by todays standards. It should run on about any octane you can get at the pump. I am not a fan of ethanol, so I use non-ethanol fuel, which can be easy or hard to find depending on where you live.