Update. I had a look at the sites suggested... lots of stuff out there for these old trucks. I also looked the front retainer and screw or labyrinth seal over well... it all looked good. Also no practical way to add a positive seal.

I did notice there was no vent of any kind. I concluded the oil leak was either from extreme angle operation or heat and pressure pushing it out.

I made a vent using one of the top cover bolts... drilled it through and mounted a generic transmission vent on the head. It goes right through to the inside so its vented now.

Feltons clutch service in Chattanooga turned around a refaced clutch in a day and upped pressure plate spring pressure for good measure.

All together and works well. Now if it just stays that way