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I switched to carb and when the truck is warmed up it is really hard to start. The only way it will start is to put the gas to the floor and crank till it starts. Is this a timing issue?
600 carb
10d before
Mix is 14.5:1 @ idle
4lbs fuel pressure

I have no experience with this on a carbed setup, but on EFI when this happens, it's an indication that the engine is trying to crank lean. The most common issue is people have updated their injectors but didn't update the cranking injector PW function that dictates how much fuel gets injected based on engine coolant temp.

So as it relates to carb, my guess is it is trying to crank lean. Since carbs have an accelerator pump, I'd try pushing the throttle a few times before trying to crank and see if that makes any difference. If it does, then the carb is trying to crank the engine lean. If it makes things worse, then the carb is likely trying to crank way too rich.

And BTW, when cranking the range of AFR that will crank an engine is VERY wide. An engine will actually crank even if the mix is a tad leaner than stoic but will also turn over and crank on an AFR down to around 10:1. Now once the engine is running under its own power, you can't continue to run it down that rich particularly if the engine is warm. The colder the engine, the more fuel the engine needs on crank (hence the choke). An idle that's too rich will surge, hunt, and stumble. As the engine's pistons and valves warm over the next 20-40 seconds, the AFR needs to lean out closer to stoic. If the engine is hot (i.e. engine's been running, conked out, and needs to be immediately recranked), you should be able to crank very near stoic and immediately begin idle that low. In fact, most Ford EECs will re-enter a conk-recrank condition in Closed Loop once the engine is running again as long as the EEC hasn't been ignition power cycled since crank-enrichment isn't required in that condition.

pour a little gas down carb and see if it fires right up or remains the same. If it fires right up I would check float levels.