This is going to sound really stupid but, I had this same problem that you are describing. Check and see if the bolts / nuts that hold your carb down on the intake are tight. I never checked it and I was getting stranded evertime I would kill the truck after it got up to operating temp. After it cooled off it would start again.
I didn't find this out until I was pulling the carb off to replace it only to find that the bolts were less than finger tight on the front side. I tightened them down and fired it up let it run to operating temp, killed it and fired it right back up.... Then I put my new carb on... lol I'm lucky that the thing never burst into flames......
