Classic Winnebagos & Vintage RVs

My 68 Ford( inline six,single barrel carter carb) chassis F17 won't start.  I have fire to the spark plugs and when I give it a shot of starting fluid it runs a moment, so the beast is not getting fuel.  Where do I start tracking down the problem and how?

Now here's the rest of the story, the simple thing first, put gas in the gas tank  :-[, added about 5 gallons, saved a little to pour in the carb, it sputtered then died, tried her again and away she went, :P, I was out of gas Hm?, gas gauges just moved up the priority list.  The old 68, 6er runs fine when it has petrol. W%

Kinda weird how that works, isn't it?   ;)