10lb or 2 5lb extinguishers handy and ready for initial crankup - TRUST ME.
There is a bunch of good advice here, so I'll offer up mine - lol. Evacuate the gas tank via siphon. Add 5-10 gallons of fresh gas. Unhook the coil/ignition. Install fresh/charged battery and crank it over and see how it sounds. Crank long enough to see if the idiot light for oil pressure goes out or oil pressure gauge needle moves. Hookup ignition and see what gives. Poor some (small amount) of gas in carb to see if it will fire - lather rinse and repeat until spits to a start.
Two people make this a much safer and quicker process remembering to keep one guy nearby a fire killing implement (extinguisher).
Maybe you already posted it and I missed it, but where are you located? I do understand sentimental value, but be realistic with performance goals of this 307. I'm truly sorry to hear about your Grandfather, it sounds like you were close - as it should be. Get it running, driving and cruising.
