Weird, new problem arising..

[Bradydz]

I've got a 355 in my '64 GMC, and for the past few days, it's been having a new problem. I'll be driving just fine, no problem going a constant speed, accelerating, etc. But when I go to stop after a little while, I push the clutch in and start coasting to slow down, and all of a sudden, the engine stops. It kicks right back up when I turn the ignition to start it, and then continues to drive fine, as if nothing happened.
I'm not all that great at diagnosing problems, as I'm still learning to speak "auto". :P
Anyone have an idea of what could be happening? It's only done it 4 times in the last 4 days, and it seems to take around 15-20 minutes of driving, as it has done it near my work 3 times (which is about 10 miles), and then again tonight when I was almost home.

I will add that I do know my timing is likely off, as it likes to diesel from time to time.. Not sure if that could be a/the problem.

Thanks, guys!

[BR3W CITY]

vacuum leak. Is it cammed? If you hit the clutch, the rev's drop and the engine can't "pick back up" . When you hit the brakes (i assume power brakes) your rev's drop, and it uses what vacuum you do have for the brake booster...lack of vacuum and the truck will die at idle or deceleration.
If you have a vacuum advance distributor, the lac of vacuum could also be part of why your dieseling.

If any of that sounds like it applies to your situation, check through the old vacuum hoses and make sure nothing is broken or crumbling apart. Hit them with some starting fluid and see if the rev's jump (will let you know where the leak is)

[61K10]

what carb? possible high float level------

[xxboondockxx]

Double check distributor and alternator for loose wires. Happened to me.

[Bradydz]

I went ahead and checked my vacuum lines, and didn't find anything bad. While I was doing that, I noticed my ignition wire, and other wires that were wrapped with it, had touched my ramhorn exhaust manifold, and I saw bare wire on the ignition wire. Soon as I patched it and secured it away (I had it secured before, but my dad had been checking a few wires, and must've not put it back where I did), the problem went away. Was it probably grounding the bare wire, which shut the truck off? Either way, another problem solved!