1973 Chevy Truck Won't start

Engine Mechanical problem
1973 Chevy Truck V8 Two Wheel Drive Automatic

I just replaced the fuel pump 2 months ago, and ran flawlessly until just recently. The engine will crank, but not fire (Same symptoms it had before I replaced pump). I primed the carburator, and it started but died after the fuel ran out. Fuel pump checked out o.K, so back at square one. According to receipts from previous owner, the carb was rebuilt 19 years ago. Could this be the cause? If not, what else could it be? Thanks for your help.