After having similar issues with my rope install I went with the neoprene seal. I'm not suggesting you should give up on the rope, but my crank surface was clean, and hasn't leaked yet! (Let me quantify by saying my 235 has only run ~40 minutes since I rebuilt it!)

1949 Canadian Built Chevy 1434 (3804 US equivalent)
In the Stovebolt Gallery

1949Chevy.com - Photo blog describing the teardown and restoration

AD Radio Rebuild