I am having difficulties keeping my '53 235 running. I have re-built the carb, replaced inline fuel filters, and tested the fuel pump. Everything appears to be fine. The only way she'll start is to but gas down the carb to prime it. Once started, runs good at idle. Once on the road, makes it about 2 blocks and dies. Re-prime, and another 2 blocks. I am stumped. Any ideas to what I did wrong?

1949 1.5 Ton 4400, 1969 c10, 1989 c1500, 1990 K2500, 2010 C1500 Crew