Fuel would be a good bet, but I had a similar fault on an AQ150 - turned out to be a duff condenser in the ignition. Would start and run for a few mins, then cut out and refuse to start. Leave for a while (talking an hour or so) and get the same start then stop.
Took me ages chasing fuel pumps, lines and filters to finally discover it was the condenser. Less than £10 to buy, 15 mins to fit. Peasy
I have often found that V8's are a bit sluggish from cold, usually because the fuel in the float chamber has evaporated from heat soak after the last shutdown, my 350 Magnum always needs a few cranks to fill the float bowl, then a few good full throttle pumps to squirt some neat fuel in and she fires up, the keep the revs at around 1500 until it gets warm and the choke goes off.
And because of the heat soak problem I find that hotstart can be a problem as the fuel vapour has filled the inlet manifold so there is no air, the solution is to open the throttle fully and crank to get some air in there and when she catches smartly pull it back to idle.
Well i had her running again on sunday, she ran for about 10 minutes before deciding to stop! One thing i have noticed is a strong smell of fuel after she decides to cut out, with a fair bit of visible fume coming from the breather tubes, close to where they attatch to the air filter/flame arrestor? Any help appreciated as always.