Front seals

[37 truck]

I got my 1940 flathead running following a complete rebuild, and everything has gone right except after about 50 miles the one piece front seal is leaking. When I slow or go to stop it leaves a stream of oil on the pavement. This is as the oil in the pan moves forward. We had put a reddi sleave on the pully shaft. Now I get to drop the pan and replace the seal. Should I go back to a two piece seal, or try another one piece seal? Thoughts? It is a PITA!