I'll be following this one closely as my 51 does something similar. I still have the old harness and sending unit, to be replaced one day.... Let us know if you get it resolved, ill probably need to troubleshoot mine when I get to it.

Thanks!

1951 Chevrolet 1/2 Ton
http://s2.photobucket.com/albums/y7/pikappa167/1951%20Chevy/