Truck idles terribly and has a little trouble starting

I have a 1975 Dodge W100 Powerwagon with a 1969 318 from a case combine. It has been an ongoing project since I got it last year. I got it to pull my boat and paid $700 so it's not exactly is pristine condition. Anyway, I have tried everything I can think of but it still idles very badly. If the engine is cold it won't idle at all, it will die the second my foot leaves the gas pedal. If the engine is hot it will usually stay alive for a few minutes, but it will sputter a little and you can here it surging. If it doesn't die immediately it sounds like it will almost stall out then it will rev and little and it does this for a few minutes until it dies. It doesn't do this when your driving just when it's not moving. The other problem is it takes a little while to fire. You crank it about five times, then you stop and it will fire the second time you try to start it. It hardly ever fires the first time I try to start it. The engine fairly well after you get to about 25 m.P.H, and gets a little worse the slower you go. I have replaced and checked about everything I can think of. Here's the list; starter, plugs (yes I gapped them), plug wires, points (gapped them to), rotor, condenser, fuel pump, air filter, fuel line to carb, fuel filter, I have the idle all the way up on the carb, and the carb has good vacuum, the fuel lines are not rusted. I don't want to have to pay to rebuild the carb, so any ideas beside that?