83 Blazer problems.....HELP!!

I have an 83 K5 blazer with a 454 and I have been having a problem I can not figure out. My car stutters and stalls out after it has been running for more than 15-20 minutes. It does it when I am accelerating and more so when it is hot outside( I live in Phoenix, Az). As far as I can tell it is not getting gas properly. When it stalls out it is hard to start unless I prime it by pouring some gas directly to the carb. So far I have replaced the fuel pump, fuel line, fuel filter, carb, coil, ignition module, distributor cap, as well as some vaccum hoses. I still have the problem everyday. Sometimes it will stutter and try to stall out and sometimes it does stall. I can not figure out what is going on and it is driving me crazy. I dont know if it is vapor locking or maybe the vaccum pump is bad?? I have owned the car for 8 years and have never had this problem until rececntly. If anyone can offer any suggestions I would really appreciate the help.

Ever done a tuneup?

Thats the next thing on the list.

Should be the first. ;)